Allocate RAM for guest VM in vmd(8) and pass it to vmm(4)

vmm(4) then maps the pages allocated by the vmd(8) user process into the
address space of the guest. This gives vmm(4) and vmd(8) a shared view of
the guest RAM. This will allow us to have faster guest<->host data
exchange by ordinary memory loads/stores later, as well as remove the
vm_readpage and vm_writepage ioctls next.

ok mlarkin@

1 files changed, 63 insertions, 6 deletions

diff --git a/usr.sbin/vmd/vmm.c b/usr.sbin/vmd/vmm.c
index 4ae471a3835..458d341281c 100644
--- a/usr.sbin/vmd/vmm.c
+++ b/usr.sbin/vmd/vmm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vmm.c,v 1.26 2016/04/07 05:51:26 guenther Exp $	*/
+/*	$OpenBSD: vmm.c,v 1.27 2016/06/07 16:19:06 stefan Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -22,6 +22,7 @@
 #include <sys/uio.h>
 #include <sys/socket.h>
 #include <sys/time.h>
+#include <sys/mman.h>
 
 #include <dev/ic/comreg.h>
 #include <dev/ic/i8253reg.h>
@@ -111,6 +112,7 @@ void *vcpu_run_loop(void *);
 int vcpu_exit(struct vm_run_params *);
 int vcpu_reset(uint32_t, uint32_t, struct vcpu_init_state *);
 void create_memory_map(struct vm_create_params *);
+int alloc_guest_mem(struct vm_create_params *);
 int vmm_create_vm(struct vm_create_params *);
 void init_emulated_hw(struct vm_create_params *, int *, int *);
 void vcpu_exit_inout(struct vm_run_params *);
@@ -465,6 +467,12 @@ start_vm(struct imsg *imsg, uint32_t *id)
 		log_procinit(vcp->vcp_name);
 
 		create_memory_map(vcp);
+		ret = alloc_guest_mem(vcp);
+		if (ret) {
+			errno = ret;
+			fatal("could not allocate guest memory - exiting");
+		}
+
 		ret = vmm_create_vm(vcp);
 		current_vm = vm;
 
@@ -647,20 +655,20 @@ start_client_vmd(void)
 void
 create_memory_map(struct vm_create_params *vcp)
 {
-	size_t mem_mb;
-	uint64_t mem_bytes, len;
+	size_t len, mem_bytes, mem_mb;
 
 	mem_mb = vcp->vcp_memranges[0].vmr_size;
 	vcp->vcp_nmemranges = 0;
 	if (mem_mb < 1 || mem_mb > VMM_MAX_VM_MEM_SIZE)
 		return;
 
-	mem_bytes = (uint64_t)mem_mb * 1024 * 1024;
+	mem_bytes = mem_mb * 1024 * 1024;
 
 	/* First memory region: 0 - LOWMEM_KB (DOS low mem) */
+	len = LOWMEM_KB * 1024;
 	vcp->vcp_memranges[0].vmr_gpa = 0x0;
-	vcp->vcp_memranges[0].vmr_size = LOWMEM_KB * 1024;
-	mem_bytes -= LOWMEM_KB * 1024;
+	vcp->vcp_memranges[0].vmr_size = len;
+	mem_bytes -= len;
 
 	/*
 	 * Second memory region: LOWMEM_KB - 1MB.
@@ -696,6 +704,55 @@ create_memory_map(struct vm_create_params *vcp)
 }
 
 /*
+ * alloc_guest_mem
+ *
+ * Allocates memory for the guest.
+ * Instead of doing a single allocation with one mmap(), we allocate memory
+ * separately for every range for the following reasons:
+ * - ASLR for the individual ranges
+ * - to reduce memory consumption in the UVM subsystem: if vmm(4) had to
+ *   map the single mmap'd userspace memory to the individual guest physical
+ *   memory ranges, the underlying amap of the single mmap'd range would have
+ *   to allocate per-page reference counters. The reason is that the
+ *   individual guest physical ranges would reference the single mmap'd region
+ *   only partially. However, if every guest physical range has its own
+ *   corresponding mmap'd userspace allocation, there are no partial
+ *   references: every guest physical range fully references an mmap'd
+ *   range => no per-page reference counters have to be allocated.
+ *
+ * Return values:
+ *  0: success
+ *  !0: failure - errno indicating the source of the failure
+ */
+int
+alloc_guest_mem(struct vm_create_params *vcp)
+{
+	void *p;
+	int ret;
+	size_t i, j;
+	struct vm_mem_range *vmr;
+
+	for (i = 0; i < vcp->vcp_nmemranges; i++) {
+		vmr = &vcp->vcp_memranges[i];
+		p = mmap(NULL, vmr->vmr_size, PROT_READ | PROT_WRITE,
+		    MAP_PRIVATE | MAP_ANON, -1, 0);
+		if (p == MAP_FAILED) {
+			ret = errno;
+			for (j = 0; j < i; j++) {
+				vmr = &vcp->vcp_memranges[j];
+				munmap((void *)vmr->vmr_va, vmr->vmr_size);
+			}
+
+			return (ret);
+		}
+
+		vmr->vmr_va = (vaddr_t)p;
+	}
+
+	return (0);
+}
+
+/*
  * vmm_create_vm
  *
  * Requests vmm(4) to create a new VM using the supplied creation