[PATCH] KVM: MMU: If emulating an instruction fails, try unprotecting the page

A page table may have been recycled into a regular page, and so any
instruction can be executed on it.  Unprotect the page and let the cpu do its
thing.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 047f6f6..7903243 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1063,6 +1063,8 @@
 	}
 
 	if (r) {
+		if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
+			return EMULATE_DONE;
 		if (!vcpu->mmio_needed) {
 			report_emulation_failure(&emulate_ctxt);
 			return EMULATE_FAIL;