[PATCH] KVM: MMU: Page table write flood protection

In fork() (or when we protect a page that is no longer a page table), we can
experience floods of writes to a page, which have to be emulated.  This is
expensive.

So, if we detect such a flood, zap the page so subsequent writes can proceed
natively.

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>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 6e4daf404146..201b2735ca91 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -238,6 +238,9 @@ struct kvm_vcpu {
         struct kvm_mmu_page page_header_buf[KVM_NUM_MMU_PAGES];
         struct kvm_mmu mmu;
 
+        gfn_t last_pt_write_gfn;
+        int   last_pt_write_count;
+
         struct kvm_guest_debug guest_debug;
 
         char fx_buf[FX_BUF_SIZE];