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-rw-r--r--arch/x86/kvm/mmu.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fa3486d6407..dd20b199a7c 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);