[PATCH] KVM: MMU: Implement simple reverse mapping

Keep in each host page frame's page->private a pointer to the shadow pte which
maps it.  If there are multiple shadow ptes mapping the page, set bit 0 of
page->private, and use the rest as a pointer to a linked list of all such
mappings.

Reverse mappings are needed because we when we cache shadow page tables, we
must protect the guest page tables from being modified by the guest, as that
would invalidate the cached ptes.

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>

drivers/kvm/kvm.h

@@ -236,6 +236,7 @@ struct kvm {
 	struct kvm_vcpu vcpus[KVM_MAX_VCPUS];
 	int memory_config_version;
 	int busy;
+	unsigned long rmap_overflow;
 };
 
 struct kvm_stat {