vmm: [snapshot] MTRR should be saved/restored

Ubuntu 22.04 (Linux 5.15.0-84-generic) gets panic (hangs) if do:

 1. Snapshot VM while it is in GRUB menu
 2. Resume
 3. Boot Linux.

Linux dmesg:

  total RAM covered: 1M
  gran_size: 64K  chunk_size: 64K         num_reg: 4      lose cover RAM: 92K
  ...
  mtrr_cleanup: can not find optimal value
  please specify mtrr_gran_size/mtrr_chunk_size
  WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 510MB of RAM.
  WARNING: CPU: 0 PID: 0 at arch/x86/kernel/cpu/mtrr/cleanup.c:978
                              mtrr_trim_uncached_memory+0x426/0x469
  ...
  BUG: unable to handle page fault for address: ffff9d0047e15ff8

-
Adding MTTR increases kernel dump size for 256 bytes per vCPU:
-

Sponsored by:		vStack
Differential Revision:	https://reviews.freebsd.org/D43226

sys/amd64/vmm/amd/svm.c

@@ -2781,6 +2781,8 @@ svm_vcpu_snapshot(void *vcpui, struct vm_snapshot_meta *meta)
 	SNAPSHOT_VAR_OR_LEAVE(vcpu->asid.gen, meta, err, done);
 	SNAPSHOT_VAR_OR_LEAVE(vcpu->asid.num, meta, err, done);
 
+	SNAPSHOT_BUF_OR_LEAVE(&vcpu->mtrr, sizeof(vcpu->mtrr), meta, err, done);
+
 	/* Set all caches dirty */
 	if (meta->op == VM_SNAPSHOT_RESTORE)
 		svm_set_dirty(vcpu, 0xffffffff);

sys/amd64/vmm/intel/vmx.c

@@ -4200,6 +4200,9 @@ vmx_vcpu_snapshot(void *vcpui, struct vm_snapshot_meta *meta)
 	SNAPSHOT_BUF_OR_LEAVE(vcpu->pir_desc,
 	    sizeof(*vcpu->pir_desc), meta, err, done);
 
+	SNAPSHOT_BUF_OR_LEAVE(&vcpu->mtrr,
+	    sizeof(vcpu->mtrr), meta, err, done);
+
 	vmxctx = &vcpu->ctx;
 	SNAPSHOT_VAR_OR_LEAVE(vmxctx->guest_rdi, meta, err, done);
 	SNAPSHOT_VAR_OR_LEAVE(vmxctx->guest_rsi, meta, err, done);