[PATCH] KVM: X86: MMU: no mmu_notifier_seq++ in kvm_age_hva

Peter Feiner
2016-09-26T17:45:53Z

The MMU notifier sequence number keeps GPA->HPA mappings in sync when
GPA->HPA lookups are done outside of the MMU lock (e.g., in
tdp_page_fault). Since kvm_age_hva doesn't change GPA->HPA, it's
unnecessary to increment the sequence number.

Signed-off-by: Peter Feiner <pfeiner@google.com>
---
arch/x86/kvm/mmu.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3d4cc8cc..dc6d1e8 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1660,17 +1660,9 @@ int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
* This has some overhead, but not as much as the cost of swapping
* out actively used pages or breaking up actively used hugepages.
*/
- if (!shadow_accessed_mask) {
- /*
- * We are holding the kvm->mmu_lock, and we are blowing up
- * shadow PTEs. MMU notifier consumers need to be kept at bay.
- * This is correct as long as we don't decouple the mmu_lock
- * protected regions (like invalidate_range_start|end does).
- */
- kvm->mmu_notifier_seq++;
+ if (!shadow_accessed_mask)
return kvm_handle_hva_range(kvm, start, end, 0,
kvm_unmap_rmapp);
- }

return kvm_handle_hva_range(kvm, start, end, 0, kvm_age_rmapp);
}
--
2.8.0.rc3.226.g39d4020