lib/libkvm: add kvm_read test

[alfredo]

Summary

This adds a sanity check for the value received from kvm_read. Test will fail if value is different from the expected one.

This derived from work in D23776

Test Plan

run TestSuite on powerpc64 and amd64

[jhibbits]

Can you also test this on amd64?

[ngie]

One thing that isn't clear is why this sanity check is needed. Is this being specifically for platform integration issue with PowerPC64, or is there another better reason for why this needs to be done given the API? If for the latter reason and the item is well-documented, please add it. If not, this doesn't seem to serve much value and might be better implemented as a platform-specific regression test.

Please test this on amd64 as well as a sanity check, second.

lib/libkvm/tests/kvm_geterr_test.c

30 ↗

(On Diff #68640)

This doesn't follow style(9).

1. sys/types.h isn't needed if sys/param.h is present.
2. sys/sysctl.h should be below sys/param.h // sys/types.h .

[ngie]

In D23783#523422, @ngie wrote:

One thing that isn't clear is why this sanity check is needed. Is this being specifically for platform integration issue with PowerPC64, or is there another better reason for why this needs to be done given the API? If for the latter reason and the item is well-documented, please add it. If not, this doesn't seem to serve much value and might be better implemented as a platform-specific regression test.

Please test this on amd64 as well as a sanity check, second.

I sent an update to my previous comment that I wanted to note via email as well for clarity. I included it above.

[jhb]

lib/libkvm/tests/kvm_geterr_test.c

131 ↗

(On Diff #68640)

I think verifying that kvm_Read() is returning the correct value is probably a decent test, and it should work on all platforms (mp_maxcpus is MI after all).

I think sticking it in this test is probably a bit dubious though. I know it would require some code duplication, but I think this should be a standalone test of kvm_read rather than part of this test for kvm_geterr.

[ngie]

lib/libkvm/tests/kvm_geterr_test.c

131 ↗

(On Diff #68640)

@jhb: agreed.

[alfredo]

In D23783#523422, @ngie wrote:

One thing that isn't clear is why this sanity check is needed. Is this being specifically for platform integration issue with PowerPC64, or is there another better reason for why this needs to be done given the API? If for the latter reason and the item is well-documented, please add it. If not, this doesn't seem to serve much value and might be better implemented as a platform-specific regression test.

Please test this on amd64 as well as a sanity check, second.

I added the test because while creating D23776 I initially prevented panic but while trying to understand the data returned I figured out the initial solution was completelly wrong. So I think a sanity check of the value would help us to quickly detect regression on both kvm_read and /dev/kmem read consequently. As suggested, I will rework this as a new test case.

It looks like the variable is not platform specific. I will double check the results on amd64.

lib/libkvm/tests/kvm_geterr_test.c

131 ↗

(On Diff #68640)

Sure, I'm going to create a new test for this check.

[alfredo]

Hi @ngie are you ok with the new "kvm_read_test" test?
I tested it on powerpc64 and amd64

[jhb]

lib/libkvm/tests/kvm_read_test.c

48 ↗

(On Diff #68902)

This test doesn't need kvm_open2(). You can just use kvm_open() instead as that works fine for native. kvm_open2() is only needed to support cross-debugging of vmcores.

89 ↗

(On Diff #68902)

This seems odd to test, and it requires you to abuse _kvm_err(). I think it would be better to just not bother testing this. Just as errno is only valid after an error, kvm_geterr() is only valid to call if you have an error. I would argue that calling it after success in this case is undefined behavior, so not something worth testing.

[alfredo]

use kvm_open instead of kvm_open2

[alfredo]

Remove call to internal API _kvm_err after reviewer's comment

[alfredo]

@ngie, @jhb do you think it's ok to merge now? Thanks!

lib/libkvm/tests/kvm_read_test.c

89 ↗

(On Diff #68902)

Sure, this was based on another test, but I agree removing it.

head/lib/libkvm/tests/Makefile

 #include <pthread.h>
 #include <pthread_np.h>
 #include <signal.h>
 #include <sysexits.h>
 #include <unistd.h>
 
 #include <machine/atomic.h>
 
+#include <sys/linker_set.h>
+
 #include "bhyverun.h"
 #include "debug.h"
 #include "mevent.h"
-#include "block_if.h"
+#include "block_backends.h"
 
-#define BLOCKIF_SIG     0xb109b109
+SET_DECLARE(block_backend_set, block_backend_t);
 
-#define BLOCKIF_NUMTHR  8
-#define BLOCKIF_MAXREQ  (BLOCKIF_RING_MAX + BLOCKIF_NUMTHR)
-
-enum blockop {
-        BOP_READ,
-        BOP_WRITE,
-        BOP_FLUSH,
-        BOP_DELETE
-};
-
-enum blockstat {
-        BST_FREE,
-        BST_BLOCK,
-        BST_PEND,
-        BST_BUSY,
-        BST_DONE
-};
-
-struct blockif_elem {
-        TAILQ_ENTRY(blockif_elem) be_link;
-        struct blockif_req  *be_req;
-        enum blockop         be_op;
-        enum blockstat       be_status;
-        pthread_t            be_tid;
-        off_t                be_block;
-};
-
-struct blockif_ctxt {
-        int                     bc_magic;
-        int                     bc_fd;
-        int                     bc_ischr;
-        int                     bc_isgeom;
-        int                     bc_candelete;
-        int                     bc_rdonly;
-        off_t                   bc_size;
-        int                     bc_sectsz;
-        int                     bc_psectsz;
-        int                     bc_psectoff;
-        int                     bc_closing;
-        pthread_t               bc_btid[BLOCKIF_NUMTHR];
-        pthread_mutex_t         bc_mtx;
-        pthread_cond_t          bc_cond;
-
-        /* Request elements and free/pending/busy queues */
-        TAILQ_HEAD(, blockif_elem) bc_freeq;       
-        TAILQ_HEAD(, blockif_elem) bc_pendq;
-        TAILQ_HEAD(, blockif_elem) bc_busyq;
-        struct blockif_elem     bc_reqs[BLOCKIF_MAXREQ];
-};
-
-static pthread_once_t blockif_once = PTHREAD_ONCE_INIT;
-
-struct blockif_sig_elem {
-        pthread_mutex_t                 bse_mtx;
-        pthread_cond_t                  bse_cond;
-        int                             bse_pending;
-        struct blockif_sig_elem         *bse_next;
-};
-
-static struct blockif_sig_elem *blockif_bse_head;
-
-static int
-blockif_enqueue(struct blockif_ctxt *bc, struct blockif_req *breq,
-                enum blockop op)
-{
-        struct blockif_elem *be, *tbe;
-        off_t off;
-        int i;
-
-        be = TAILQ_FIRST(&bc->bc_freeq);
-        assert(be != NULL);
-        assert(be->be_status == BST_FREE);
-        TAILQ_REMOVE(&bc->bc_freeq, be, be_link);
-        be->be_req = breq;
-        be->be_op = op;
-        switch (op) {
-        case BOP_READ:
-        case BOP_WRITE:
-        case BOP_DELETE:
-                off = breq->br_offset;
-                for (i = 0; i < breq->br_iovcnt; i++)
-                        off += breq->br_iov[i].iov_len;
-                break;
-        default:
-                off = OFF_MAX;
-        }
-        be->be_block = off;
-        TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
-                if (tbe->be_block == breq->br_offset)
-                        break;
-        }
-        if (tbe == NULL) {
-                TAILQ_FOREACH(tbe, &bc->bc_busyq, be_link) {
-                        if (tbe->be_block == breq->br_offset)
-                                break;
-                }
-        }
-        if (tbe == NULL)
-                be->be_status = BST_PEND;
-        else
-                be->be_status = BST_BLOCK;
-        TAILQ_INSERT_TAIL(&bc->bc_pendq, be, be_link);
-        return (be->be_status == BST_PEND);
-}
-
-static int
-blockif_dequeue(struct blockif_ctxt *bc, pthread_t t, struct blockif_elem **bep)
-{
-        struct blockif_elem *be;
-
-        TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
-                if (be->be_status == BST_PEND)
-                        break;
-                assert(be->be_status == BST_BLOCK);
-        }
-        if (be == NULL)
-                return (0);
-        TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
-        be->be_status = BST_BUSY;
-        be->be_tid = t;
-        TAILQ_INSERT_TAIL(&bc->bc_busyq, be, be_link);
-        *bep = be;
-        return (1);
-}
-
-static void
-blockif_complete(struct blockif_ctxt *bc, struct blockif_elem *be)
-{
-        struct blockif_elem *tbe;
-
-        if (be->be_status == BST_DONE || be->be_status == BST_BUSY)
-                TAILQ_REMOVE(&bc->bc_busyq, be, be_link);
-        else
-                TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
-        TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
-                if (tbe->be_req->br_offset == be->be_block)
-                        tbe->be_status = BST_PEND;
-        }
-        be->be_tid = 0;
-        be->be_status = BST_FREE;
-        be->be_req = NULL;
-        TAILQ_INSERT_TAIL(&bc->bc_freeq, be, be_link);
-}
-
-static void
-blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be, uint8_t *buf)
-{
-        struct blockif_req *br;
-        off_t arg[2];
-        ssize_t clen, len, off, boff, voff;
-        int i, err;
-
-        br = be->be_req;
-        if (br->br_iovcnt <= 1)
-                buf = NULL;
-        err = 0;
-        switch (be->be_op) {
-        case BOP_READ:
-                if (buf == NULL) {
-                        if ((len = preadv(bc->bc_fd, br->br_iov, br->br_iovcnt,
-                                   br->br_offset)) < 0)
-                                err = errno;
-                        else
-                                br->br_resid -= len;
-                        break;
-                }
-                i = 0;
-                off = voff = 0;
-                while (br->br_resid > 0) {
-                        len = MIN(br->br_resid, MAXPHYS);
-                        if (pread(bc->bc_fd, buf, len, br->br_offset +
-                            off) < 0) {
-                                err = errno;
-                                break;
-                        }
-                        boff = 0;
-                        do {
-                                clen = MIN(len - boff, br->br_iov[i].iov_len -
-                                    voff);
-                                memcpy(br->br_iov[i].iov_base + voff,
-                                    buf + boff, clen);
-                                if (clen < br->br_iov[i].iov_len - voff)
-                                        voff += clen;
-                                else {
-                                        i++;
-                                        voff = 0;
-                                }
-                                boff += clen;
-                        } while (boff < len);
-                        off += len;
-                        br->br_resid -= len;
-                }
-                break;
-        case BOP_WRITE:
-                if (bc->bc_rdonly) {
-                        err = EROFS;
-                        break;
-                }
-                if (buf == NULL) {
-                        if ((len = pwritev(bc->bc_fd, br->br_iov, br->br_iovcnt,
-                                    br->br_offset)) < 0)
-                                err = errno;
-                        else
-                                br->br_resid -= len;
-                        break;
-                }
-                i = 0;
-                off = voff = 0;
-                while (br->br_resid > 0) {
-                        len = MIN(br->br_resid, MAXPHYS);
-                        boff = 0;
-                        do {
-                                clen = MIN(len - boff, br->br_iov[i].iov_len -
-                                    voff);
-                                memcpy(buf + boff,
-                                    br->br_iov[i].iov_base + voff, clen);
-                                if (clen < br->br_iov[i].iov_len - voff)
-                                        voff += clen;
-                                else {
-                                        i++;
-                                        voff = 0;
-                                }
-                                boff += clen;
-                        } while (boff < len);
-                        if (pwrite(bc->bc_fd, buf, len, br->br_offset +
-                            off) < 0) {
-                                err = errno;
-                                break;
-                        }
-                        off += len;
-                        br->br_resid -= len;
-                }
-                break;
-        case BOP_FLUSH:
-                if (bc->bc_ischr) {
-                        if (ioctl(bc->bc_fd, DIOCGFLUSH))
-                                err = errno;
-                } else if (fsync(bc->bc_fd))
-                        err = errno;
-                break;
-        case BOP_DELETE:
-                if (!bc->bc_candelete)
-                        err = EOPNOTSUPP;
-                else if (bc->bc_rdonly)
-                        err = EROFS;
-                else if (bc->bc_ischr) {
-                        arg[0] = br->br_offset;
-                        arg[1] = br->br_resid;
-                        if (ioctl(bc->bc_fd, DIOCGDELETE, arg))
-                                err = errno;
-                        else
-                                br->br_resid = 0;
-                } else
-                        err = EOPNOTSUPP;
-                break;
-        default:
-                err = EINVAL;
-                break;
-        }
-
-        be->be_status = BST_DONE;
-
-        (*br->br_callback)(br, err);
-}
-
-static void *
-blockif_thr(void *arg)
-{
-        struct blockif_ctxt *bc;
-        struct blockif_elem *be;
-        pthread_t t;
-        uint8_t *buf;
-
-        bc = arg;
-        if (bc->bc_isgeom)
-                buf = malloc(MAXPHYS);
-        else
-                buf = NULL;
-        t = pthread_self();
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        for (;;) {
-                while (blockif_dequeue(bc, t, &be)) {
-                        pthread_mutex_unlock(&bc->bc_mtx);
-                        blockif_proc(bc, be, buf);
-                        pthread_mutex_lock(&bc->bc_mtx);
-                        blockif_complete(bc, be);
-                }
-                /* Check ctxt status here to see if exit requested */
-                if (bc->bc_closing)
-                        break;
-                pthread_cond_wait(&bc->bc_cond, &bc->bc_mtx);
-        }
-        pthread_mutex_unlock(&bc->bc_mtx);
-
-        if (buf)
-                free(buf);
-        pthread_exit(NULL);
-        return (NULL);
-}
-
-static void
-blockif_sigcont_handler(int signal, enum ev_type type, void *arg)
-{
-        struct blockif_sig_elem *bse;
-
-        for (;;) {
-                /*
-                 * Process the entire list even if not intended for
-                 * this thread.
-                 */
-                do {
-                        bse = blockif_bse_head;
-                        if (bse == NULL)
-                                return;
-                } while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
-                                            (uintptr_t)bse,
-                                            (uintptr_t)bse->bse_next));
-
-                pthread_mutex_lock(&bse->bse_mtx);
-                bse->bse_pending = 0;
-                pthread_cond_signal(&bse->bse_cond);
-                pthread_mutex_unlock(&bse->bse_mtx);
-        }
-}
-
-static void
-blockif_init(void)
+ * Initialize a backend and attach to the frontend.
+ * This is called during frontend initialization.
+ *  @pbe is a pointer to the backend to be initialized
+ *  @devname is the backend-name as supplied on the command line,
+ *      e.g. -s 2:0,frontend-name,backend-name[,other-args]
+ *  @cb is the receive callback supplied by the frontend,
+ *      and it is invoked in the event loop when a receive
+ *      event is generated in the hypervisor,
+ *  @param is a pointer to the frontend, and normally used as
+ *      the argument for the callback.
+int 
+blockbe_open(block_backend_t **ret, const char *optstr, 
+             const char *pci_ident)
 {
-        mevent_add(SIGCONT, EVF_SIGNAL, blockif_sigcont_handler, NULL);
-        (void) signal(SIGCONT, SIG_IGN);
-}
+    block_backend_t **bbe = NULL;
+    int err;
+    *ret = NULL;
 
-struct blockif_ctxt *
-blockif_open(const char *optstr, const char *ident)
-{
-        char tname[MAXCOMLEN + 1];
-        char name[MAXPATHLEN];
-        char *nopt, *xopts, *cp;
-        struct blockif_ctxt *bc;
-        struct stat sbuf;
-        struct diocgattr_arg arg;
-        off_t size, psectsz, psectoff;
-        int extra, fd, i, sectsz;
-        int nocache, sync, ro, candelete, geom, ssopt, pssopt;
-#ifndef WITHOUT_CAPSICUM
-        cap_rights_t rights;
-        cap_ioctl_t cmds[] = { DIOCGFLUSH, DIOCGDELETE };
-#endif
-
-        pthread_once(&blockif_once, blockif_init);
-
-        fd = -1;
-        ssopt = 0;
-        nocache = 0;
-        sync = 0;
-        ro = 0;
-
-        /*
-         * The first element in the optstring is always a pathname.
-         * Optional elements follow
-         */
-        nopt = xopts = strdup(optstr);
-        while (xopts != NULL) {
-                cp = strsep(&xopts, ",");
-                if (cp == nopt)                /* file or device pathname */
-                        continue;
-                else if (!strcmp(cp, "nocache"))
-                        nocache = 1;
-                else if (!strcmp(cp, "sync") || !strcmp(cp, "direct"))
-                        sync = 1;
-                else if (!strcmp(cp, "ro"))
-                        ro = 1;
-                else if (sscanf(cp, "sectorsize=%d/%d", &ssopt, &pssopt) == 2)
-                        ;
-                else if (sscanf(cp, "sectorsize=%d", &ssopt) == 1)
-                        pssopt = ssopt;
-                else {
-                        EPRINTLN("Invalid device option \"%s\"", cp);
-                        goto err;
-                }
-        }
+    /*
+     * Find the block device backend that matches the user-provided
+     * device name. block_backend_set is built using a linker set.
+     */
+    SET_FOREACH(bbe, block_backend_set) {
     
-        extra = 0;
-        if (nocache)
-                extra |= O_DIRECT;
-        if (sync)
-                extra |= O_SYNC;
-
-        fd = open(nopt, (ro ? O_RDONLY : O_RDWR) | extra);
-        if (fd < 0 && !ro) {
-                /* Attempt a r/w fail with a r/o open */
-                fd = open(nopt, O_RDONLY | extra);
-                ro = 1;
-        }
-
-        if (fd < 0) {
-                warn("Could not open backing file: %s", nopt);
-                goto err;
-        }
-
-        if (fstat(fd, &sbuf) < 0) {
-                warn("Could not stat backing file %s", nopt);
-                goto err;
-        }
-
-#ifndef WITHOUT_CAPSICUM
-        cap_rights_init(&rights, CAP_FSYNC, CAP_IOCTL, CAP_READ, CAP_SEEK,
-            CAP_WRITE);
-        if (ro)
-                cap_rights_clear(&rights, CAP_FSYNC, CAP_WRITE);
-
-        if (caph_rights_limit(fd, &rights) == -1)
-                errx(EX_OSERR, "Unable to apply rights for sandbox");
-#endif
-
-        /*
-         * Deal with raw devices
+        /* 
+         * How do we find the appropriate open for each backend? 
+         * We should itterate over all block_open() functions until one
+         * returns true as an indication that it accepts the give descriptor
+         * in opstr
          */
-        size = sbuf.st_size;
-        sectsz = DEV_BSIZE;
-        psectsz = psectoff = 0;
-        candelete = geom = 0;
-        if (S_ISCHR(sbuf.st_mode)) {
-                if (ioctl(fd, DIOCGMEDIASIZE, &size) < 0 ||
-                    ioctl(fd, DIOCGSECTORSIZE, &sectsz)) {
-                        perror("Could not fetch dev blk/sector size");
-                        goto err;
-                }
-                assert(size != 0);
-                assert(sectsz != 0);
-                if (ioctl(fd, DIOCGSTRIPESIZE, &psectsz) == 0 && psectsz > 0)
-                        ioctl(fd, DIOCGSTRIPEOFFSET, &psectoff);
-                strlcpy(arg.name, "GEOM::candelete", sizeof(arg.name));
-                arg.len = sizeof(arg.value.i);
-                if (ioctl(fd, DIOCGATTR, &arg) == 0)
-                        candelete = arg.value.i;
-                if (ioctl(fd, DIOCGPROVIDERNAME, name) == 0)
-                        geom = 1;
-        } else
-                psectsz = sbuf.st_blksize;
-
-#ifndef WITHOUT_CAPSICUM
-        if (caph_ioctls_limit(fd, cmds, nitems(cmds)) == -1)
-                errx(EX_OSERR, "Unable to apply rights for sandbox");
-#endif
-
-        if (ssopt != 0) {
-                if (!powerof2(ssopt) || !powerof2(pssopt) || ssopt < 512 ||
-                    ssopt > pssopt) {
-                        EPRINTLN("Invalid sector size %d/%d",
-                            ssopt, pssopt);
-                        goto err;
-                }
-
-                /*
-                 * Some backend drivers (e.g. cd0, ada0) require that the I/O
-                 * size be a multiple of the device's sector size.
-                 *
-                 * Validate that the emulated sector size complies with this
-                 * requirement.
-                 */
-                if (S_ISCHR(sbuf.st_mode)) {
-                        if (ssopt < sectsz || (ssopt % sectsz) != 0) {
-                                EPRINTLN("Sector size %d incompatible "
-                                    "with underlying device sector size %d",
-                                    ssopt, sectsz);
-                                goto err;
-                        }
-                }
-
-                sectsz = ssopt;
-                psectsz = pssopt;
-                psectoff = 0;
-        }
+         * Local access has a pattern like:
+         *   3:0,virtio-blk,file/somewhere/guest.img
+         *   3:0,virtio-blk,/dev/xxxx
+         * The file part should be in optstr so we check if optstr exists as a file 
+         * in which case it would be access to the local filesystem.
+         * This is handled by the blk-local backend.
+         * If this does not match then other backends in the block_backend_set have 
+         * their open() called. The first one returning 0 is a match and is used
+         * with the specification in optstr
+         * 
+        if ((err = (*bbe)->open(ret, optstr, pci_ident)) == 0) {
+            break;
+        }
+    }
+    return err;
 
-        bc = calloc(1, sizeof(struct blockif_ctxt));
-        if (bc == NULL) {
-                perror("calloc");
-                goto err;
-        }
+off_t
+blockbe_size(block_backend_t *be)
+{
+    assert(be != NULL);
+    return (be->size(be));
 
-        bc->bc_magic = BLOCKIF_SIG;
-        bc->bc_fd = fd;
-        bc->bc_ischr = S_ISCHR(sbuf.st_mode);
-        bc->bc_isgeom = geom;
-        bc->bc_candelete = candelete;
-        bc->bc_rdonly = ro;
-        bc->bc_size = size;
-        bc->bc_sectsz = sectsz;
-        bc->bc_psectsz = psectsz;
-        bc->bc_psectoff = psectoff;
-        pthread_mutex_init(&bc->bc_mtx, NULL);
-        pthread_cond_init(&bc->bc_cond, NULL);
-        TAILQ_INIT(&bc->bc_freeq);
-        TAILQ_INIT(&bc->bc_pendq);
-        TAILQ_INIT(&bc->bc_busyq);
-        for (i = 0; i < BLOCKIF_MAXREQ; i++) {
-                bc->bc_reqs[i].be_status = BST_FREE;
-                TAILQ_INSERT_HEAD(&bc->bc_freeq, &bc->bc_reqs[i], be_link);
-        }
-
-        for (i = 0; i < BLOCKIF_NUMTHR; i++) {
-                pthread_create(&bc->bc_btid[i], NULL, blockif_thr, bc);
-                snprintf(tname, sizeof(tname), "blk-%s-%d", ident, i);
-                pthread_set_name_np(bc->bc_btid[i], tname);
-        }
-
-        return (bc);
-err:
-        if (fd >= 0)
-                close(fd);
-        free(nopt);
-        return (NULL);
-}
-
-static int
-blockif_request(struct blockif_ctxt *bc, struct blockif_req *breq,
-                enum blockop op)
+void
+blockbe_chs(block_backend_t *be, uint16_t *c, uint8_t *h, 
+    uint8_t *s)
 {
-        int err;
-
-        err = 0;
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        if (!TAILQ_EMPTY(&bc->bc_freeq)) {
-                /*
-                 * Enqueue and inform the block i/o thread
-                 * that there is work available
-                 */
-                if (blockif_enqueue(bc, breq, op))
-                        pthread_cond_signal(&bc->bc_cond);
-        } else {
-                /*
-                 * Callers are not allowed to enqueue more than
-                 * the specified blockif queue limit. Return an
-                 * error to indicate that the queue length has been
-                 * exceeded.
-                 */
-                err = E2BIG;
-        }
-        pthread_mutex_unlock(&bc->bc_mtx);
+    assert(be != NULL);
+    (be->chs(be, c, h, s));
 
-        return (err);
-}
-
 int
-blockif_read(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_sectsz(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_READ));
+    assert(be != NULL);
+    return (be->sectsz(be));
 }
 
-int
-blockif_write(struct blockif_ctxt *bc, struct blockif_req *breq)
+void
+blockbe_psectsz(block_backend_t *be, int *size, int *off)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_WRITE));
+    assert(be != NULL);
+    return (be->psectsz(be, size, off));
 }
 
 int
-blockif_flush(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_queuesz(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_FLUSH));
+    assert(be != NULL);
+    return (be->queuesz(be));
 }
 
 int
-blockif_delete(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_is_ro(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_DELETE));
+    assert(be != NULL);
+    return (be->is_ro(be));
 }
 
 int
-blockif_cancel(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_candelete(block_backend_t *be)
 {
-        struct blockif_elem *be;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        /*
-         * Check pending requests.
-         */
-        TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
-                if (be->be_req == breq)
-                        break;
-        }
-        if (be != NULL) {
-                /*
-                 * Found it.
-                 */
-                blockif_complete(bc, be);
-                pthread_mutex_unlock(&bc->bc_mtx);
+    assert(be != NULL);
+    return (be->candelete(be));
 
-                return (0);
-        }
-
-        /*
-         * Check in-flight requests.
-         */
-        TAILQ_FOREACH(be, &bc->bc_busyq, be_link) {
-                if (be->be_req == breq)
-                        break;
-        }
-        if (be == NULL) {
-                /*
-                 * Didn't find it.
-                 */
-                pthread_mutex_unlock(&bc->bc_mtx);
-                return (EINVAL);
-        }
-
-        /*
-         * Interrupt the processing thread to force it return
-         * prematurely via it's normal callback path.
-         */
-        while (be->be_status == BST_BUSY) {
-                struct blockif_sig_elem bse, *old_head;
-
-                pthread_mutex_init(&bse.bse_mtx, NULL);
-                pthread_cond_init(&bse.bse_cond, NULL);
-
-                bse.bse_pending = 1;
-
-                do {
-                        old_head = blockif_bse_head;
-                        bse.bse_next = old_head;
-                } while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
-                                            (uintptr_t)old_head,
-                                            (uintptr_t)&bse));
-
-                pthread_kill(be->be_tid, SIGCONT);
-
-                pthread_mutex_lock(&bse.bse_mtx);
-                while (bse.bse_pending)
-                        pthread_cond_wait(&bse.bse_cond, &bse.bse_mtx);
-                pthread_mutex_unlock(&bse.bse_mtx);
-        }
-
-        pthread_mutex_unlock(&bc->bc_mtx);
-
-        /*
-         * The processing thread has been interrupted.  Since it's not
-         * clear if the callback has been invoked yet, return EBUSY.
-         */
-        return (EBUSY);
-}
-
 int
-blockif_close(struct blockif_ctxt *bc)
+blockbe_read(block_backend_t *be, struct blockif_req *breq)
 {
-        void *jval;
-        int i;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        /*
-         * Stop the block i/o thread
-         */
-        pthread_mutex_lock(&bc->bc_mtx);
-        bc->bc_closing = 1;
-        pthread_mutex_unlock(&bc->bc_mtx);
-        pthread_cond_broadcast(&bc->bc_cond);
-        for (i = 0; i < BLOCKIF_NUMTHR; i++)
-                pthread_join(bc->bc_btid[i], &jval);
-
-        /* XXX Cancel queued i/o's ??? */
-
-        /*
-         * Release resources
-         */
-        bc->bc_magic = 0;
-        close(bc->bc_fd);
-        free(bc);
-
-        return (0);
+    assert(be != NULL);
+    return (be->read(be, breq));
 }
 
-/*
- * Return virtual C/H/S values for a given block. Use the algorithm
- * outlined in the VHD specification to calculate values.
- */
-void
-blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h, uint8_t *s)
+int
+blockbe_write(block_backend_t *be, struct blockif_req *breq)
 {
-        off_t sectors;                /* total sectors of the block dev */
-        off_t hcyl;                /* cylinders times heads */
-        uint16_t secpt;         /* sectors per track */
-        uint8_t heads;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        sectors = bc->bc_size / bc->bc_sectsz;
-
-        /* Clamp the size to the largest possible with CHS */
-        if (sectors > 65535UL*16*255)
-                sectors = 65535UL*16*255;
-
-        if (sectors >= 65536UL*16*63) {
-                secpt = 255;
-                heads = 16;
-                hcyl = sectors / secpt;
-        } else {
-                secpt = 17;
-                hcyl = sectors / secpt;
-                heads = (hcyl + 1023) / 1024;
-
-                if (heads < 4)
-                        heads = 4;
-
-                if (hcyl >= (heads * 1024) || heads > 16) {
-                        secpt = 31;
-                        heads = 16;
-                        hcyl = sectors / secpt;
-                }
-                if (hcyl >= (heads * 1024)) {
-                        secpt = 63;
-                        heads = 16;
-                        hcyl = sectors / secpt;
-                }
-        }
+    assert(be != NULL);
+    return (be->write(be, breq));
 
-        *c = hcyl / heads;
-        *h = heads;
-        *s = secpt;
-}
-
-/*
- * Accessors
- */
-off_t
-blockif_size(struct blockif_ctxt *bc)
-{
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_size);
-}
-
 int
-blockif_sectsz(struct blockif_ctxt *bc)
+blockbe_flush(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_sectsz);
+    assert(be != NULL);
+    return (be->flush(be, breq));
 }
 
-void
-blockif_psectsz(struct blockif_ctxt *bc, int *size, int *off)
-{
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        *size = bc->bc_psectsz;
-        *off = bc->bc_psectoff;
-}
-
 int
-blockif_queuesz(struct blockif_ctxt *bc)
+blockbe_delete(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (BLOCKIF_MAXREQ - 1);
+    assert(be != NULL);
+    return (be->delete(be, breq));
 }
 
 int
-blockif_is_ro(struct blockif_ctxt *bc)
+blockbe_cancel(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_rdonly);
+    assert(be != NULL);
+    return (be->cancel(be, breq));
 }
 
 int
-blockif_candelete(struct blockif_ctxt *bc)
+blockbe_close(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_candelete);
+    assert(be != NULL);
+    return (be->close(be));
 }

head/lib/libkvm/tests/kvm_read_test.c

 #include <pthread.h>
 #include <pthread_np.h>
 #include <signal.h>
 #include <sysexits.h>
 #include <unistd.h>
 
 #include <machine/atomic.h>
 
+#include <sys/linker_set.h>
+
 #include "bhyverun.h"
 #include "debug.h"
 #include "mevent.h"
-#include "block_if.h"
+#include "block_backends.h"
 
-#define BLOCKIF_SIG     0xb109b109
+SET_DECLARE(block_backend_set, block_backend_t);
 
-#define BLOCKIF_NUMTHR  8
-#define BLOCKIF_MAXREQ  (BLOCKIF_RING_MAX + BLOCKIF_NUMTHR)
-
-enum blockop {
-        BOP_READ,
-        BOP_WRITE,
-        BOP_FLUSH,
-        BOP_DELETE
-};
-
-enum blockstat {
-        BST_FREE,
-        BST_BLOCK,
-        BST_PEND,
-        BST_BUSY,
-        BST_DONE
-};
-
-struct blockif_elem {
-        TAILQ_ENTRY(blockif_elem) be_link;
-        struct blockif_req  *be_req;
-        enum blockop         be_op;
-        enum blockstat       be_status;
-        pthread_t            be_tid;
-        off_t                be_block;
-};
-
-struct blockif_ctxt {
-        int                     bc_magic;
-        int                     bc_fd;
-        int                     bc_ischr;
-        int                     bc_isgeom;
-        int                     bc_candelete;
-        int                     bc_rdonly;
-        off_t                   bc_size;
-        int                     bc_sectsz;
-        int                     bc_psectsz;
-        int                     bc_psectoff;
-        int                     bc_closing;
-        pthread_t               bc_btid[BLOCKIF_NUMTHR];
-        pthread_mutex_t         bc_mtx;
-        pthread_cond_t          bc_cond;
-
-        /* Request elements and free/pending/busy queues */
-        TAILQ_HEAD(, blockif_elem) bc_freeq;       
-        TAILQ_HEAD(, blockif_elem) bc_pendq;
-        TAILQ_HEAD(, blockif_elem) bc_busyq;
-        struct blockif_elem     bc_reqs[BLOCKIF_MAXREQ];
-};
-
-static pthread_once_t blockif_once = PTHREAD_ONCE_INIT;
-
-struct blockif_sig_elem {
-        pthread_mutex_t                 bse_mtx;
-        pthread_cond_t                  bse_cond;
-        int                             bse_pending;
-        struct blockif_sig_elem         *bse_next;
-};
-
-static struct blockif_sig_elem *blockif_bse_head;
-
-static int
-blockif_enqueue(struct blockif_ctxt *bc, struct blockif_req *breq,
-                enum blockop op)
-{
-        struct blockif_elem *be, *tbe;
-        off_t off;
-        int i;
-
-        be = TAILQ_FIRST(&bc->bc_freeq);
-        assert(be != NULL);
-        assert(be->be_status == BST_FREE);
-        TAILQ_REMOVE(&bc->bc_freeq, be, be_link);
-        be->be_req = breq;
-        be->be_op = op;
-        switch (op) {
-        case BOP_READ:
-        case BOP_WRITE:
-        case BOP_DELETE:
-                off = breq->br_offset;
-                for (i = 0; i < breq->br_iovcnt; i++)
-                        off += breq->br_iov[i].iov_len;
-                break;
-        default:
-                off = OFF_MAX;
-        }
-        be->be_block = off;
-        TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
-                if (tbe->be_block == breq->br_offset)
-                        break;
-        }
-        if (tbe == NULL) {
-                TAILQ_FOREACH(tbe, &bc->bc_busyq, be_link) {
-                        if (tbe->be_block == breq->br_offset)
-                                break;
-                }
-        }
-        if (tbe == NULL)
-                be->be_status = BST_PEND;
-        else
-                be->be_status = BST_BLOCK;
-        TAILQ_INSERT_TAIL(&bc->bc_pendq, be, be_link);
-        return (be->be_status == BST_PEND);
-}
-
-static int
-blockif_dequeue(struct blockif_ctxt *bc, pthread_t t, struct blockif_elem **bep)
-{
-        struct blockif_elem *be;
-
-        TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
-                if (be->be_status == BST_PEND)
-                        break;
-                assert(be->be_status == BST_BLOCK);
-        }
-        if (be == NULL)
-                return (0);
-        TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
-        be->be_status = BST_BUSY;
-        be->be_tid = t;
-        TAILQ_INSERT_TAIL(&bc->bc_busyq, be, be_link);
-        *bep = be;
-        return (1);
-}
-
-static void
-blockif_complete(struct blockif_ctxt *bc, struct blockif_elem *be)
-{
-        struct blockif_elem *tbe;
-
-        if (be->be_status == BST_DONE || be->be_status == BST_BUSY)
-                TAILQ_REMOVE(&bc->bc_busyq, be, be_link);
-        else
-                TAILQ_REMOVE(&bc->bc_pendq, be, be_link);
-        TAILQ_FOREACH(tbe, &bc->bc_pendq, be_link) {
-                if (tbe->be_req->br_offset == be->be_block)
-                        tbe->be_status = BST_PEND;
-        }
-        be->be_tid = 0;
-        be->be_status = BST_FREE;
-        be->be_req = NULL;
-        TAILQ_INSERT_TAIL(&bc->bc_freeq, be, be_link);
-}
-
-static void
-blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be, uint8_t *buf)
-{
-        struct blockif_req *br;
-        off_t arg[2];
-        ssize_t clen, len, off, boff, voff;
-        int i, err;
-
-        br = be->be_req;
-        if (br->br_iovcnt <= 1)
-                buf = NULL;
-        err = 0;
-        switch (be->be_op) {
-        case BOP_READ:
-                if (buf == NULL) {
-                        if ((len = preadv(bc->bc_fd, br->br_iov, br->br_iovcnt,
-                                   br->br_offset)) < 0)
-                                err = errno;
-                        else
-                                br->br_resid -= len;
-                        break;
-                }
-                i = 0;
-                off = voff = 0;
-                while (br->br_resid > 0) {
-                        len = MIN(br->br_resid, MAXPHYS);
-                        if (pread(bc->bc_fd, buf, len, br->br_offset +
-                            off) < 0) {
-                                err = errno;
-                                break;
-                        }
-                        boff = 0;
-                        do {
-                                clen = MIN(len - boff, br->br_iov[i].iov_len -
-                                    voff);
-                                memcpy(br->br_iov[i].iov_base + voff,
-                                    buf + boff, clen);
-                                if (clen < br->br_iov[i].iov_len - voff)
-                                        voff += clen;
-                                else {
-                                        i++;
-                                        voff = 0;
-                                }
-                                boff += clen;
-                        } while (boff < len);
-                        off += len;
-                        br->br_resid -= len;
-                }
-                break;
-        case BOP_WRITE:
-                if (bc->bc_rdonly) {
-                        err = EROFS;
-                        break;
-                }
-                if (buf == NULL) {
-                        if ((len = pwritev(bc->bc_fd, br->br_iov, br->br_iovcnt,
-                                    br->br_offset)) < 0)
-                                err = errno;
-                        else
-                                br->br_resid -= len;
-                        break;
-                }
-                i = 0;
-                off = voff = 0;
-                while (br->br_resid > 0) {
-                        len = MIN(br->br_resid, MAXPHYS);
-                        boff = 0;
-                        do {
-                                clen = MIN(len - boff, br->br_iov[i].iov_len -
-                                    voff);
-                                memcpy(buf + boff,
-                                    br->br_iov[i].iov_base + voff, clen);
-                                if (clen < br->br_iov[i].iov_len - voff)
-                                        voff += clen;
-                                else {
-                                        i++;
-                                        voff = 0;
-                                }
-                                boff += clen;
-                        } while (boff < len);
-                        if (pwrite(bc->bc_fd, buf, len, br->br_offset +
-                            off) < 0) {
-                                err = errno;
-                                break;
-                        }
-                        off += len;
-                        br->br_resid -= len;
-                }
-                break;
-        case BOP_FLUSH:
-                if (bc->bc_ischr) {
-                        if (ioctl(bc->bc_fd, DIOCGFLUSH))
-                                err = errno;
-                } else if (fsync(bc->bc_fd))
-                        err = errno;
-                break;
-        case BOP_DELETE:
-                if (!bc->bc_candelete)
-                        err = EOPNOTSUPP;
-                else if (bc->bc_rdonly)
-                        err = EROFS;
-                else if (bc->bc_ischr) {
-                        arg[0] = br->br_offset;
-                        arg[1] = br->br_resid;
-                        if (ioctl(bc->bc_fd, DIOCGDELETE, arg))
-                                err = errno;
-                        else
-                                br->br_resid = 0;
-                } else
-                        err = EOPNOTSUPP;
-                break;
-        default:
-                err = EINVAL;
-                break;
-        }
-
-        be->be_status = BST_DONE;
-
-        (*br->br_callback)(br, err);
-}
-
-static void *
-blockif_thr(void *arg)
-{
-        struct blockif_ctxt *bc;
-        struct blockif_elem *be;
-        pthread_t t;
-        uint8_t *buf;
-
-        bc = arg;
-        if (bc->bc_isgeom)
-                buf = malloc(MAXPHYS);
-        else
-                buf = NULL;
-        t = pthread_self();
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        for (;;) {
-                while (blockif_dequeue(bc, t, &be)) {
-                        pthread_mutex_unlock(&bc->bc_mtx);
-                        blockif_proc(bc, be, buf);
-                        pthread_mutex_lock(&bc->bc_mtx);
-                        blockif_complete(bc, be);
-                }
-                /* Check ctxt status here to see if exit requested */
-                if (bc->bc_closing)
-                        break;
-                pthread_cond_wait(&bc->bc_cond, &bc->bc_mtx);
-        }
-        pthread_mutex_unlock(&bc->bc_mtx);
-
-        if (buf)
-                free(buf);
-        pthread_exit(NULL);
-        return (NULL);
-}
-
-static void
-blockif_sigcont_handler(int signal, enum ev_type type, void *arg)
-{
-        struct blockif_sig_elem *bse;
-
-        for (;;) {
-                /*
-                 * Process the entire list even if not intended for
-                 * this thread.
-                 */
-                do {
-                        bse = blockif_bse_head;
-                        if (bse == NULL)
-                                return;
-                } while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
-                                            (uintptr_t)bse,
-                                            (uintptr_t)bse->bse_next));
-
-                pthread_mutex_lock(&bse->bse_mtx);
-                bse->bse_pending = 0;
-                pthread_cond_signal(&bse->bse_cond);
-                pthread_mutex_unlock(&bse->bse_mtx);
-        }
-}
-
-static void
-blockif_init(void)
+ * Initialize a backend and attach to the frontend.
+ * This is called during frontend initialization.
+ *  @pbe is a pointer to the backend to be initialized
+ *  @devname is the backend-name as supplied on the command line,
+ *      e.g. -s 2:0,frontend-name,backend-name[,other-args]
+ *  @cb is the receive callback supplied by the frontend,
+ *      and it is invoked in the event loop when a receive
+ *      event is generated in the hypervisor,
+ *  @param is a pointer to the frontend, and normally used as
+ *      the argument for the callback.
+int 
+blockbe_open(block_backend_t **ret, const char *optstr, 
+             const char *pci_ident)
 {
-        mevent_add(SIGCONT, EVF_SIGNAL, blockif_sigcont_handler, NULL);
-        (void) signal(SIGCONT, SIG_IGN);
-}
+    block_backend_t **bbe = NULL;
+    int err;
+    *ret = NULL;
 
-struct blockif_ctxt *
-blockif_open(const char *optstr, const char *ident)
-{
-        char tname[MAXCOMLEN + 1];
-        char name[MAXPATHLEN];
-        char *nopt, *xopts, *cp;
-        struct blockif_ctxt *bc;
-        struct stat sbuf;
-        struct diocgattr_arg arg;
-        off_t size, psectsz, psectoff;
-        int extra, fd, i, sectsz;
-        int nocache, sync, ro, candelete, geom, ssopt, pssopt;
-#ifndef WITHOUT_CAPSICUM
-        cap_rights_t rights;
-        cap_ioctl_t cmds[] = { DIOCGFLUSH, DIOCGDELETE };
-#endif
-
-        pthread_once(&blockif_once, blockif_init);
-
-        fd = -1;
-        ssopt = 0;
-        nocache = 0;
-        sync = 0;
-        ro = 0;
-
-        /*
-         * The first element in the optstring is always a pathname.
-         * Optional elements follow
-         */
-        nopt = xopts = strdup(optstr);
-        while (xopts != NULL) {
-                cp = strsep(&xopts, ",");
-                if (cp == nopt)                /* file or device pathname */
-                        continue;
-                else if (!strcmp(cp, "nocache"))
-                        nocache = 1;
-                else if (!strcmp(cp, "sync") || !strcmp(cp, "direct"))
-                        sync = 1;
-                else if (!strcmp(cp, "ro"))
-                        ro = 1;
-                else if (sscanf(cp, "sectorsize=%d/%d", &ssopt, &pssopt) == 2)
-                        ;
-                else if (sscanf(cp, "sectorsize=%d", &ssopt) == 1)
-                        pssopt = ssopt;
-                else {
-                        EPRINTLN("Invalid device option \"%s\"", cp);
-                        goto err;
-                }
-        }
+    /*
+     * Find the block device backend that matches the user-provided
+     * device name. block_backend_set is built using a linker set.
+     */
+    SET_FOREACH(bbe, block_backend_set) {
     
-        extra = 0;
-        if (nocache)
-                extra |= O_DIRECT;
-        if (sync)
-                extra |= O_SYNC;
-
-        fd = open(nopt, (ro ? O_RDONLY : O_RDWR) | extra);
-        if (fd < 0 && !ro) {
-                /* Attempt a r/w fail with a r/o open */
-                fd = open(nopt, O_RDONLY | extra);
-                ro = 1;
-        }
-
-        if (fd < 0) {
-                warn("Could not open backing file: %s", nopt);
-                goto err;
-        }
-
-        if (fstat(fd, &sbuf) < 0) {
-                warn("Could not stat backing file %s", nopt);
-                goto err;
-        }
-
-#ifndef WITHOUT_CAPSICUM
-        cap_rights_init(&rights, CAP_FSYNC, CAP_IOCTL, CAP_READ, CAP_SEEK,
-            CAP_WRITE);
-        if (ro)
-                cap_rights_clear(&rights, CAP_FSYNC, CAP_WRITE);
-
-        if (caph_rights_limit(fd, &rights) == -1)
-                errx(EX_OSERR, "Unable to apply rights for sandbox");
-#endif
-
-        /*
-         * Deal with raw devices
+        /* 
+         * How do we find the appropriate open for each backend? 
+         * We should itterate over all block_open() functions until one
+         * returns true as an indication that it accepts the give descriptor
+         * in opstr
          */
-        size = sbuf.st_size;
-        sectsz = DEV_BSIZE;
-        psectsz = psectoff = 0;
-        candelete = geom = 0;
-        if (S_ISCHR(sbuf.st_mode)) {
-                if (ioctl(fd, DIOCGMEDIASIZE, &size) < 0 ||
-                    ioctl(fd, DIOCGSECTORSIZE, &sectsz)) {
-                        perror("Could not fetch dev blk/sector size");
-                        goto err;
-                }
-                assert(size != 0);
-                assert(sectsz != 0);
-                if (ioctl(fd, DIOCGSTRIPESIZE, &psectsz) == 0 && psectsz > 0)
-                        ioctl(fd, DIOCGSTRIPEOFFSET, &psectoff);
-                strlcpy(arg.name, "GEOM::candelete", sizeof(arg.name));
-                arg.len = sizeof(arg.value.i);
-                if (ioctl(fd, DIOCGATTR, &arg) == 0)
-                        candelete = arg.value.i;
-                if (ioctl(fd, DIOCGPROVIDERNAME, name) == 0)
-                        geom = 1;
-        } else
-                psectsz = sbuf.st_blksize;
-
-#ifndef WITHOUT_CAPSICUM
-        if (caph_ioctls_limit(fd, cmds, nitems(cmds)) == -1)
-                errx(EX_OSERR, "Unable to apply rights for sandbox");
-#endif
-
-        if (ssopt != 0) {
-                if (!powerof2(ssopt) || !powerof2(pssopt) || ssopt < 512 ||
-                    ssopt > pssopt) {
-                        EPRINTLN("Invalid sector size %d/%d",
-                            ssopt, pssopt);
-                        goto err;
-                }
-
-                /*
-                 * Some backend drivers (e.g. cd0, ada0) require that the I/O
-                 * size be a multiple of the device's sector size.
-                 *
-                 * Validate that the emulated sector size complies with this
-                 * requirement.
-                 */
-                if (S_ISCHR(sbuf.st_mode)) {
-                        if (ssopt < sectsz || (ssopt % sectsz) != 0) {
-                                EPRINTLN("Sector size %d incompatible "
-                                    "with underlying device sector size %d",
-                                    ssopt, sectsz);
-                                goto err;
-                        }
-                }
-
-                sectsz = ssopt;
-                psectsz = pssopt;
-                psectoff = 0;
-        }
+         * Local access has a pattern like:
+         *   3:0,virtio-blk,file/somewhere/guest.img
+         *   3:0,virtio-blk,/dev/xxxx
+         * The file part should be in optstr so we check if optstr exists as a file 
+         * in which case it would be access to the local filesystem.
+         * This is handled by the blk-local backend.
+         * If this does not match then other backends in the block_backend_set have 
+         * their open() called. The first one returning 0 is a match and is used
+         * with the specification in optstr
+         * 
+        if ((err = (*bbe)->open(ret, optstr, pci_ident)) == 0) {
+            break;
+        }
+    }
+    return err;
 
-        bc = calloc(1, sizeof(struct blockif_ctxt));
-        if (bc == NULL) {
-                perror("calloc");
-                goto err;
-        }
+off_t
+blockbe_size(block_backend_t *be)
+{
+    assert(be != NULL);
+    return (be->size(be));
 
-        bc->bc_magic = BLOCKIF_SIG;
-        bc->bc_fd = fd;
-        bc->bc_ischr = S_ISCHR(sbuf.st_mode);
-        bc->bc_isgeom = geom;
-        bc->bc_candelete = candelete;
-        bc->bc_rdonly = ro;
-        bc->bc_size = size;
-        bc->bc_sectsz = sectsz;
-        bc->bc_psectsz = psectsz;
-        bc->bc_psectoff = psectoff;
-        pthread_mutex_init(&bc->bc_mtx, NULL);
-        pthread_cond_init(&bc->bc_cond, NULL);
-        TAILQ_INIT(&bc->bc_freeq);
-        TAILQ_INIT(&bc->bc_pendq);
-        TAILQ_INIT(&bc->bc_busyq);
-        for (i = 0; i < BLOCKIF_MAXREQ; i++) {
-                bc->bc_reqs[i].be_status = BST_FREE;
-                TAILQ_INSERT_HEAD(&bc->bc_freeq, &bc->bc_reqs[i], be_link);
-        }
-
-        for (i = 0; i < BLOCKIF_NUMTHR; i++) {
-                pthread_create(&bc->bc_btid[i], NULL, blockif_thr, bc);
-                snprintf(tname, sizeof(tname), "blk-%s-%d", ident, i);
-                pthread_set_name_np(bc->bc_btid[i], tname);
-        }
-
-        return (bc);
-err:
-        if (fd >= 0)
-                close(fd);
-        free(nopt);
-        return (NULL);
-}
-
-static int
-blockif_request(struct blockif_ctxt *bc, struct blockif_req *breq,
-                enum blockop op)
+void
+blockbe_chs(block_backend_t *be, uint16_t *c, uint8_t *h, 
+    uint8_t *s)
 {
-        int err;
-
-        err = 0;
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        if (!TAILQ_EMPTY(&bc->bc_freeq)) {
-                /*
-                 * Enqueue and inform the block i/o thread
-                 * that there is work available
-                 */
-                if (blockif_enqueue(bc, breq, op))
-                        pthread_cond_signal(&bc->bc_cond);
-        } else {
-                /*
-                 * Callers are not allowed to enqueue more than
-                 * the specified blockif queue limit. Return an
-                 * error to indicate that the queue length has been
-                 * exceeded.
-                 */
-                err = E2BIG;
-        }
-        pthread_mutex_unlock(&bc->bc_mtx);
+    assert(be != NULL);
+    (be->chs(be, c, h, s));
 
-        return (err);
-}
-
 int
-blockif_read(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_sectsz(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_READ));
+    assert(be != NULL);
+    return (be->sectsz(be));
 }
 
-int
-blockif_write(struct blockif_ctxt *bc, struct blockif_req *breq)
+void
+blockbe_psectsz(block_backend_t *be, int *size, int *off)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_WRITE));
+    assert(be != NULL);
+    return (be->psectsz(be, size, off));
 }
 
 int
-blockif_flush(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_queuesz(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_FLUSH));
+    assert(be != NULL);
+    return (be->queuesz(be));
 }
 
 int
-blockif_delete(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_is_ro(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (blockif_request(bc, breq, BOP_DELETE));
+    assert(be != NULL);
+    return (be->is_ro(be));
 }
 
 int
-blockif_cancel(struct blockif_ctxt *bc, struct blockif_req *breq)
+blockbe_candelete(block_backend_t *be)
 {
-        struct blockif_elem *be;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        pthread_mutex_lock(&bc->bc_mtx);
-        /*
-         * Check pending requests.
-         */
-        TAILQ_FOREACH(be, &bc->bc_pendq, be_link) {
-                if (be->be_req == breq)
-                        break;
-        }
-        if (be != NULL) {
-                /*
-                 * Found it.
-                 */
-                blockif_complete(bc, be);
-                pthread_mutex_unlock(&bc->bc_mtx);
+    assert(be != NULL);
+    return (be->candelete(be));
 
-                return (0);
-        }
-
-        /*
-         * Check in-flight requests.
-         */
-        TAILQ_FOREACH(be, &bc->bc_busyq, be_link) {
-                if (be->be_req == breq)
-                        break;
-        }
-        if (be == NULL) {
-                /*
-                 * Didn't find it.
-                 */
-                pthread_mutex_unlock(&bc->bc_mtx);
-                return (EINVAL);
-        }
-
-        /*
-         * Interrupt the processing thread to force it return
-         * prematurely via it's normal callback path.
-         */
-        while (be->be_status == BST_BUSY) {
-                struct blockif_sig_elem bse, *old_head;
-
-                pthread_mutex_init(&bse.bse_mtx, NULL);
-                pthread_cond_init(&bse.bse_cond, NULL);
-
-                bse.bse_pending = 1;
-
-                do {
-                        old_head = blockif_bse_head;
-                        bse.bse_next = old_head;
-                } while (!atomic_cmpset_ptr((uintptr_t *)&blockif_bse_head,
-                                            (uintptr_t)old_head,
-                                            (uintptr_t)&bse));
-
-                pthread_kill(be->be_tid, SIGCONT);
-
-                pthread_mutex_lock(&bse.bse_mtx);
-                while (bse.bse_pending)
-                        pthread_cond_wait(&bse.bse_cond, &bse.bse_mtx);
-                pthread_mutex_unlock(&bse.bse_mtx);
-        }
-
-        pthread_mutex_unlock(&bc->bc_mtx);
-
-        /*
-         * The processing thread has been interrupted.  Since it's not
-         * clear if the callback has been invoked yet, return EBUSY.
-         */
-        return (EBUSY);
-}
-
 int
-blockif_close(struct blockif_ctxt *bc)
+blockbe_read(block_backend_t *be, struct blockif_req *breq)
 {
-        void *jval;
-        int i;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        /*
-         * Stop the block i/o thread
-         */
-        pthread_mutex_lock(&bc->bc_mtx);
-        bc->bc_closing = 1;
-        pthread_mutex_unlock(&bc->bc_mtx);
-        pthread_cond_broadcast(&bc->bc_cond);
-        for (i = 0; i < BLOCKIF_NUMTHR; i++)
-                pthread_join(bc->bc_btid[i], &jval);
-
-        /* XXX Cancel queued i/o's ??? */
-
-        /*
-         * Release resources
-         */
-        bc->bc_magic = 0;
-        close(bc->bc_fd);
-        free(bc);
-
-        return (0);
+    assert(be != NULL);
+    return (be->read(be, breq));
 }
 
-/*
- * Return virtual C/H/S values for a given block. Use the algorithm
- * outlined in the VHD specification to calculate values.
- */
-void
-blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h, uint8_t *s)
+int
+blockbe_write(block_backend_t *be, struct blockif_req *breq)
 {
-        off_t sectors;                /* total sectors of the block dev */
-        off_t hcyl;                /* cylinders times heads */
-        uint16_t secpt;         /* sectors per track */
-        uint8_t heads;
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-
-        sectors = bc->bc_size / bc->bc_sectsz;
-
-        /* Clamp the size to the largest possible with CHS */
-        if (sectors > 65535UL*16*255)
-                sectors = 65535UL*16*255;
-
-        if (sectors >= 65536UL*16*63) {
-                secpt = 255;
-                heads = 16;
-                hcyl = sectors / secpt;
-        } else {
-                secpt = 17;
-                hcyl = sectors / secpt;
-                heads = (hcyl + 1023) / 1024;
-
-                if (heads < 4)
-                        heads = 4;
-
-                if (hcyl >= (heads * 1024) || heads > 16) {
-                        secpt = 31;
-                        heads = 16;
-                        hcyl = sectors / secpt;
-                }
-                if (hcyl >= (heads * 1024)) {
-                        secpt = 63;
-                        heads = 16;
-                        hcyl = sectors / secpt;
-                }
-        }
+    assert(be != NULL);
+    return (be->write(be, breq));
 
-        *c = hcyl / heads;
-        *h = heads;
-        *s = secpt;
-}
-
-/*
- * Accessors
- */
-off_t
-blockif_size(struct blockif_ctxt *bc)
-{
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_size);
-}
-
 int
-blockif_sectsz(struct blockif_ctxt *bc)
+blockbe_flush(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_sectsz);
+    assert(be != NULL);
+    return (be->flush(be, breq));
 }
 
-void
-blockif_psectsz(struct blockif_ctxt *bc, int *size, int *off)
-{
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        *size = bc->bc_psectsz;
-        *off = bc->bc_psectoff;
-}
-
 int
-blockif_queuesz(struct blockif_ctxt *bc)
+blockbe_delete(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (BLOCKIF_MAXREQ - 1);
+    assert(be != NULL);
+    return (be->delete(be, breq));
 }
 
 int
-blockif_is_ro(struct blockif_ctxt *bc)
+blockbe_cancel(block_backend_t *be, struct blockif_req *breq)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_rdonly);
+    assert(be != NULL);
+    return (be->cancel(be, breq));
 }
 
 int
-blockif_candelete(struct blockif_ctxt *bc)
+blockbe_close(block_backend_t *be)
 {
-
-        assert(bc->bc_magic == BLOCKIF_SIG);
-        return (bc->bc_candelete);
+    assert(be != NULL);
+    return (be->close(be));
 }