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Index: head/sys/amd64/include/vmm.h
===================================================================
--- head/sys/amd64/include/vmm.h
+++ head/sys/amd64/include/vmm.h
@@ -546,6 +546,9 @@
struct vie {
uint8_t inst[VIE_INST_SIZE]; /* instruction bytes */
uint8_t num_valid; /* size of the instruction */
+
+/* The following fields are all zeroed upon restart. */
+#define vie_startzero num_processed
uint8_t num_processed;
uint8_t addrsize:4, opsize:4; /* address and operand sizes */
Index: head/sys/amd64/include/vmm_instruction_emul.h
===================================================================
--- head/sys/amd64/include/vmm_instruction_emul.h
+++ head/sys/amd64/include/vmm_instruction_emul.h
@@ -105,6 +105,7 @@
uint64_t gla, int prot, uint64_t *gpa, int *is_fault);
#endif /* _KERNEL */
+void vie_restart(struct vie *vie);
void vie_init(struct vie *vie, const char *inst_bytes, int inst_length);
/*
Index: head/sys/amd64/vmm/vmm_instruction_emul.c
===================================================================
--- head/sys/amd64/vmm/vmm_instruction_emul.c
+++ head/sys/amd64/vmm/vmm_instruction_emul.c
@@ -53,7 +53,9 @@
#include <err.h>
#include <assert.h>
#include <stdbool.h>
+#include <stddef.h>
#include <stdio.h>
+#include <string.h>
#include <strings.h>
#include <vmmapi.h>
#define KASSERT(exp,msg) assert((exp))
@@ -1990,22 +1992,36 @@
return (0);
}
+/*
+ * Prepare a partially decoded vie for a 2nd attempt.
+ */
void
-vie_init(struct vie *vie, const char *inst_bytes, int inst_length)
+vie_restart(struct vie *vie)
{
- KASSERT(inst_length >= 0 && inst_length <= VIE_INST_SIZE,
- ("%s: invalid instruction length (%d)", __func__, inst_length));
+ _Static_assert(
+ offsetof(struct vie, inst) < offsetof(struct vie, vie_startzero) &&
+ offsetof(struct vie, num_valid) < offsetof(struct vie, vie_startzero),
+ "restart should not erase instruction length or contents");
- bzero(vie, sizeof(struct vie));
+ memset((char *)vie + offsetof(struct vie, vie_startzero), 0,
+ sizeof(*vie) - offsetof(struct vie, vie_startzero));
vie->base_register = VM_REG_LAST;
vie->index_register = VM_REG_LAST;
vie->segment_register = VM_REG_LAST;
+}
- if (inst_length) {
- bcopy(inst_bytes, vie->inst, inst_length);
- vie->num_valid = inst_length;
- }
+void
+vie_init(struct vie *vie, const char *inst_bytes, int inst_length)
+{
+ KASSERT(inst_length >= 0 && inst_length <= VIE_INST_SIZE,
+ ("%s: invalid instruction length (%d)", __func__, inst_length));
+
+ vie_restart(vie);
+ memset(vie->inst, 0, sizeof(vie->inst));
+ if (inst_length != 0)
+ memcpy(vie->inst, inst_bytes, inst_length);
+ vie->num_valid = inst_length;
}
#ifdef _KERNEL
Index: head/usr.sbin/bhyve/bhyverun.c
===================================================================
--- head/usr.sbin/bhyve/bhyverun.c
+++ head/usr.sbin/bhyve/bhyverun.c
@@ -80,6 +80,7 @@
#ifndef WITHOUT_CAPSICUM
#include <machine/vmm_dev.h>
#endif
+#include <machine/vmm_instruction_emul.h>
#include <vmmapi.h>
#include "bhyverun.h"
@@ -746,12 +747,26 @@
static int
vmexit_inst_emul(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
{
- int err, i;
+ int err, i, cs_d;
struct vie *vie;
+ enum vm_cpu_mode mode;
stats.vmexit_inst_emul++;
vie = &vmexit->u.inst_emul.vie;
+ if (!vie->decoded) {
+ /*
+ * Attempt to decode in userspace as a fallback. This allows
+ * updating instruction decode in bhyve without rebooting the
+ * kernel (rapid prototyping), albeit with much slower
+ * emulation.
+ */
+ vie_restart(vie);
+ mode = vmexit->u.inst_emul.paging.cpu_mode;
+ cs_d = vmexit->u.inst_emul.cs_d;
+ (void)vmm_decode_instruction(mode, cs_d, vie);
+ }
+
err = emulate_mem(ctx, *pvcpu, vmexit->u.inst_emul.gpa,
vie, &vmexit->u.inst_emul.paging);

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