KVM: MMU: fast invalidate all mmio sptes

This patch tries to introduce a very simple and scale way to invalidate
all mmio sptes - it need not walk any shadow pages and hold mmu-lock

KVM maintains a global mmio valid generation-number which is stored in
kvm->memslots.generation and every mmio spte stores the current global
generation-number into his available bits when it is created

When KVM need zap all mmio sptes, it just simply increase the global
generation-number. When guests do mmio access, KVM intercepts a MMIO #PF
then it walks the shadow page table and get the mmio spte. If the
generation-number on the spte does not equal the global generation-number,
it will go to the normal #PF handler to update the mmio spte

Since 19 bits are used to store generation-number on mmio spte, we zap all
mmio sptes when the number is round

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index ba6a19c50f27..5b59c573aba7 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -56,12 +56,15 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask);
 /*
  * Return values of handle_mmio_page_fault_common:
  * RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
- *			 directly.
+ *			directly.
+ * RET_MMIO_PF_INVALID: invalid spte is detected then let the real page
+ *			fault path update the mmio spte.
  * RET_MMIO_PF_RETRY: let CPU fault again on the address.
  * RET_MMIO_PF_BUG: bug is detected.
  */
 enum {
 	RET_MMIO_PF_EMULATE = 1,
+	RET_MMIO_PF_INVALID = 2,
 	RET_MMIO_PF_RETRY = 0,
 	RET_MMIO_PF_BUG = -1
 };