Index: lib/libvmmapi/vmmapi.c
===================================================================
--- lib/libvmmapi/vmmapi.c	(revision 265932)
+++ lib/libvmmapi/vmmapi.c	(working copy)
@@ -57,6 +57,7 @@
 	int	fd;
 	uint32_t lowmem_limit;
 	enum vm_mmap_style vms;
+	int	memflags;
 	size_t	lowmem;
 	char	*lowmem_addr;
 	size_t	highmem;
@@ -101,6 +102,7 @@
 	assert(vm != NULL);
 
 	vm->fd = -1;
+	vm->memflags = 0;
 	vm->lowmem_limit = 3 * GB;
 	vm->name = (char *)(vm + 1);
 	strcpy(vm->name, name);
@@ -180,10 +182,17 @@
 	ctx->lowmem_limit = limit;
 }
 
+void
+vm_set_memflags(struct vmctx *ctx, int flags)
+{
+
+	ctx->memflags = flags;
+}
+
 static int
 setup_memory_segment(struct vmctx *ctx, vm_paddr_t gpa, size_t len, char **addr)
 {
-	int error;
+	int error, mmap_flags;
 	struct vm_memory_segment seg;
 
 	/*
@@ -195,8 +204,11 @@
 	seg.len = len;
 	error = ioctl(ctx->fd, VM_MAP_MEMORY, &seg);
 	if (error == 0 && addr != NULL) {
-		*addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED,
-				ctx->fd, gpa);
+		mmap_flags = MAP_SHARED;
+		if ((ctx->memflags & VM_MEM_F_INCORE) == 0)
+			mmap_flags |= MAP_NOCORE;
+		*addr = mmap(NULL, len, PROT_READ | PROT_WRITE, mmap_flags,
+		    ctx->fd, gpa);
 	}
 	return (error);
 }
Index: lib/libvmmapi/vmmapi.h
===================================================================
--- lib/libvmmapi/vmmapi.h	(revision 265932)
+++ lib/libvmmapi/vmmapi.h	(working copy)
@@ -42,6 +42,8 @@
 	VM_MMAP_SPARSE,		/* mappings created on-demand */
 };
 
+#define	VM_MEM_F_INCORE	0x01	/* include guest memory in core file */
+
 int	vm_create(const char *name);
 struct vmctx *vm_open(const char *name);
 void	vm_destroy(struct vmctx *ctx);
@@ -53,6 +55,7 @@
 int	vm_get_gpa_pmap(struct vmctx *, uint64_t gpa, uint64_t *pte, int *num);
 uint32_t vm_get_lowmem_limit(struct vmctx *ctx);
 void	vm_set_lowmem_limit(struct vmctx *ctx, uint32_t limit);
+void	vm_set_memflags(struct vmctx *ctx, int flags);
 int	vm_set_desc(struct vmctx *ctx, int vcpu, int reg,
 		    uint64_t base, uint32_t limit, uint32_t access);
 int	vm_get_desc(struct vmctx *ctx, int vcpu, int reg,
Index: usr.sbin/bhyve/bhyve.8
===================================================================
--- usr.sbin/bhyve/bhyve.8	(revision 265941)
+++ usr.sbin/bhyve/bhyve.8	(working copy)
@@ -32,7 +32,7 @@
 .Nd "run a guest operating system inside a virtual machine"
 .Sh SYNOPSIS
 .Nm
-.Op Fl aehwxAHPW
+.Op Fl aehwxACHPW
 .Op Fl c Ar numcpus
 .Op Fl g Ar gdbport
 .Op Fl p Ar vcpu:hostcpu
@@ -70,6 +70,8 @@
 .It Fl c Ar numcpus
 Number of guest virtual CPUs.
 The default is 1 and the maximum is 16.
+.It Fl C
+Include guest memory in core file.
 .It Fl H
 Yield the virtual CPU thread when a HLT instruction is detected.
 If this option is not specified, virtual CPUs will use 100% of a host CPU.
Index: usr.sbin/bhyve/bhyverun.c
===================================================================
--- usr.sbin/bhyve/bhyverun.c	(revision 265941)
+++ usr.sbin/bhyve/bhyverun.c	(working copy)
@@ -134,6 +134,7 @@
 		"       -A: create an ACPI table\n"
 		"       -g: gdb port\n"
 		"       -c: # cpus (default 1)\n"
+		"       -C: include guest memory in core file\n"
 		"       -p: pin 'vcpu' to 'hostcpu'\n"
 		"       -H: vmexit from the guest on hlt\n"
 		"       -P: vmexit from the guest on pause\n"
@@ -642,19 +643,20 @@
 main(int argc, char *argv[])
 {
 	int c, error, gdb_port, err, bvmcons;
-	int max_vcpus, mptgen;
+	int dump_guest_memory, max_vcpus, mptgen;
 	struct vmctx *ctx;
 	uint64_t rip;
 	size_t memsize;
 
 	bvmcons = 0;
+	dump_guest_memory = 0;
 	progname = basename(argv[0]);
 	gdb_port = 0;
 	guest_ncpus = 1;
 	memsize = 256 * MB;
 	mptgen = 1;
 
-	while ((c = getopt(argc, argv, "abehwxAHIPWYp:g:c:s:m:l:U:")) != -1) {
+	while ((c = getopt(argc, argv, "abehwxACHIPWYp:g:c:s:m:l:U:")) != -1) {
 		switch (c) {
 		case 'a':
 			x2apic_mode = 0;
@@ -674,6 +676,9 @@
                 case 'c':
 			guest_ncpus = atoi(optarg);
 			break;
+		case 'C':
+			dump_guest_memory = 1;
+			break;
 		case 'g':
 			gdb_port = atoi(optarg);
 			break;
@@ -755,6 +760,8 @@
 
 	fbsdrun_set_capabilities(ctx, BSP);
 
+	if (dump_guest_memory)
+		vm_set_memflags(ctx, VM_MEM_F_INCORE);
 	err = vm_setup_memory(ctx, memsize, VM_MMAP_ALL);
 	if (err) {
 		fprintf(stderr, "Unable to setup memory (%d)\n", err);