Index: stand/i386/libi386/Makefile
===================================================================
--- stand/i386/libi386/Makefile
+++ stand/i386/libi386/Makefile
@@ -4,7 +4,7 @@
 
 LIB=			i386
 
-SRCS=	bio.c biosacpi.c biosdisk.c biosmem.c biospnp.c \
+SRCS=	bio.c biosacpi.c biosdisk.c biosmem.c biosmemdisk.c biospnp.c \
 	biospci.c biossmap.c bootinfo.c bootinfo32.c bootinfo64.c \
 	comconsole.c devicename.c elf32_freebsd.c \
 	elf64_freebsd.c multiboot.c multiboot_tramp.S relocater_tramp.S \
Index: stand/i386/libi386/biosmemdisk.c
===================================================================
--- /dev/null
+++ stand/i386/libi386/biosmemdisk.c
@@ -0,0 +1,100 @@
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stand.h>
+#include <machine/stdarg.h>
+#include <bootstrap.h>
+#include <btxv86.h>
+#include "libi386.h"
+
+#include "platform/acfreebsd.h"
+#include "acconfig.h"
+#define ACPI_SYSTEM_XFACE
+#include "actypes.h"
+#include "actbl.h"
+
+struct memdisk_info {
+	uint32_t mdi_13h_hook_ptr; // not included in length!
+	uint16_t mdi_length;
+	uint8_t  mdi_minor;
+	uint8_t  mdi_major;
+	char    *mdi_disk_ptr;
+	uint32_t mdi_disk_sectors;
+	uint32_t mdi_far_ptr_cmdline;
+	uint32_t mdi_old_int13h;
+	uint32_t mdi_old_int15h;
+	uint16_t mdi_dos_mem_before;
+	uint8_t  mdi_boot_loader_id;
+	uint8_t  mdi_sector_size;
+} __attribute__((packed));
+
+struct safe_13h_hook {
+	char sh_jmp[3];
+	char sh_id[8];
+	char sh_vendor[8];
+	uint16_t sh_next_offset;
+	uint16_t sh_next_segment;
+	uint32_t sh_flags;
+	uint32_t sh_mbft;
+} __attribute__((packed));
+
+/*
+ * Scan for MEMDISK virtual block devices
+ */
+
+void
+biosmemdisk_detect()
+{
+	char line[80], scratch[80];
+	int idx, hook = 0, count = 0, sector_size;
+	uint16_t segment, offset;
+	struct safe_13h_hook *probe;
+	ACPI_TABLE_HEADER *mbft;
+	uint8_t *cp, sum;
+	
+	offset = *(uint16_t *)PTOV(0x4C); // int 13H handler in interrupt vector table
+	segment = *(uint16_t *)PTOV(0x4C + 2);
+	
+	while (hook < 32 && !(segment == 0 && offset == 0)) {
+		probe = (struct safe_13h_hook*)PTOV(segment * 16 + offset);
+		if (memcmp(probe->sh_id, "$INT13SF", sizeof(probe->sh_id)) == 0) {
+			if (memcmp(probe->sh_vendor, "MEMDISK ", sizeof(probe->sh_vendor)) == 0) {
+				mbft = (ACPI_TABLE_HEADER *)PTOV(probe->sh_mbft);
+				if (memcmp(mbft->Signature, "mBFT", sizeof(mbft->Signature)) == 0) {
+				        cp = (uint8_t *)mbft;
+                                        sum = 0;
+                                        for (idx = 0; idx < mbft->Length; ++idx)
+                                            sum += *(cp + idx);
+                                        if (sum == 0) {
+                                            struct memdisk_info *mdi = (struct memdisk_info *)PTOV(probe->sh_mbft + sizeof(*mbft));
+                                            sector_size = 512; // assume 512 unless MEMDISK struct is from 3.71+ and is non-zero))
+                                            if (mdi->mdi_length + sizeof(mdi->mdi_13h_hook_ptr) >= sizeof(*mdi) && mdi->mdi_sector_size != 0) {
+                                            	sector_size = 1 << mdi->mdi_sector_size;
+					    }
+                                            
+                                            printf("memdisk %d.%d disk at %p (%d sectors = %d bytes)\n",
+						   mdi->mdi_major, mdi->mdi_minor,
+                                                   mdi->mdi_disk_ptr, mdi->mdi_disk_sectors, mdi->mdi_disk_sectors * sector_size);
+                                            
+                                            snprintf(line, sizeof(line), "hint.md.%d.physaddr", count);
+                                            snprintf(scratch, sizeof(scratch), "0x%08x", (vm_offset_t)mdi->mdi_disk_ptr);
+                                            setenv(line, scratch, 1);
+                                            snprintf(line, sizeof(line), "hint.md.%d.len", count);
+                                            snprintf(scratch, sizeof(scratch), "%d", mdi->mdi_disk_sectors * sector_size);
+                                            setenv(line, scratch, 1);
+                                            ++count;
+                                        }
+				}
+
+			} else {
+				printf("Found int 13h safe hook at %p, vendor %.8s\n", probe, probe->sh_vendor);
+			}
+			offset = probe->sh_next_offset;
+			segment = probe->sh_next_segment;
+		} else {
+			printf("Found int 13h unsafe hook at %p (%x:%x)\n", probe, segment, offset);
+			segment = offset = 0;
+		}
+		++hook;
+	}
+}
Index: stand/i386/libi386/libi386.h
===================================================================
--- stand/i386/libi386/libi386.h
+++ stand/i386/libi386/libi386.h
@@ -154,3 +154,5 @@
 	    vm_offset_t *kernend, int add_smap);
 
 void	pxe_enable(void *pxeinfo);
+
+void	biosmemdisk_detect(void);
Index: stand/i386/loader/main.c
===================================================================
--- stand/i386/loader/main.c
+++ stand/i386/loader/main.c
@@ -256,6 +256,9 @@
 	extract_currdev();		/* set $currdev and $loaddev */
     
 	bios_getsmap();
+	
+	/* detect MEMDISK virtual disks */
+	biosmemdisk_detect();
 
 	interact();
 
Index: sys/dev/md/md.c
===================================================================
--- sys/dev/md/md.c
+++ sys/dev/md/md.c
@@ -92,6 +92,8 @@
 #include <sys/uio.h>
 #include <sys/vnode.h>
 #include <sys/disk.h>
+#include <sys/param.h>
+#include <sys/bus.h>
 
 #include <geom/geom.h>
 #include <geom/geom_int.h>
@@ -2027,8 +2029,10 @@
 {
 	caddr_t mod;
 	u_char *ptr, *name, *type;
+	u_char scratch[40];
 	unsigned len;
 	int i;
+	vm_offset_t paddr;
 
 	/* figure out log2(NINDIR) */
 	for (i = NINDIR, nshift = -1; i; nshift++)
@@ -2068,6 +2072,23 @@
 			sx_xunlock(&md_sx);
 		}
 	}
+
+	for (i = 0; i < 32; ++i) {
+		if (resource_long_value("md", i, "physaddr", (signed long*) &paddr) != 0 ||
+		    resource_int_value("md", i, "len", (signed *)&len) != 0) {
+		
+		        break;
+		}
+		
+		ptr = (char *)pmap_map(NULL, paddr, paddr + len, VM_PROT_READ);
+		if (ptr != NULL && len != 0) {
+			sprintf(scratch, "preload%d 0x%016lx", i, paddr);
+			sx_xlock(&md_sx);
+			md_preloaded(ptr, len, scratch);
+			sx_xunlock(&md_sx);
+		}
+	}
+	
 	md_pbuf_zone = pbuf_zsecond_create("mdpbuf", nswbuf / 10);
 	status_dev = make_dev(&mdctl_cdevsw, INT_MAX, UID_ROOT, GID_WHEEL,
 	    0600, MDCTL_NAME);