1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fa3486d64078..dd20b199a7c0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1593,6 +1593,15 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
 
                 spte |= PT_WRITABLE_MASK;
 
+                /*
+                 * Optimization: for pte sync, if spte was writable the hash
+                 * lookup is unnecessary (and expensive). Write protection
+                 * is responsibility of mmu_get_page / kvm_sync_page.
+                 * Same reasoning can be applied to dirty page accounting.
+                 */
+                if (!can_unsync && is_writeble_pte(*shadow_pte))
+                        goto set_pte;
+
                 if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {
                         pgprintk("%s: found shadow page for %lx, marking ro\n",
                                  __func__, gfn);