KVM: Introduce kvm_unmap_hva_range() for kvm_mmu_notifier_invalidate_range_start()

When we tested KVM under memory pressure, with THP enabled on the host,
we noticed that MMU notifier took a long time to invalidate huge pages.

Since the invalidation was done with mmu_lock held, it not only wasted
the CPU but also made the host harder to respond.

This patch mitigates this by using kvm_handle_hva_range().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b3ce91c623e2..e2b1a159e5df 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -332,8 +332,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
          * count is also read inside the mmu_lock critical section.
          */
         kvm->mmu_notifier_count++;
-        for (; start < end; start += PAGE_SIZE)
-                need_tlb_flush |= kvm_unmap_hva(kvm, start);
+        need_tlb_flush = kvm_unmap_hva_range(kvm, start, end);
         need_tlb_flush |= kvm->tlbs_dirty;
         /* we've to flush the tlb before the pages can be freed */
         if (need_tlb_flush)