KVM: MMU: optimize pte write path if don't have protected sp
Simply return from kvm_mmu_pte_write path if no shadow page is
write-protected, then we can avoid to walk all shadow pages and hold
mmu-lock
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index aee3862..b4ae7af 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -498,6 +498,7 @@
linfo = lpage_info_slot(gfn, slot, i);
linfo->write_count += 1;
}
+ kvm->arch.indirect_shadow_pages++;
}
static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
@@ -513,6 +514,7 @@
linfo->write_count -= 1;
WARN_ON(linfo->write_count < 0);
}
+ kvm->arch.indirect_shadow_pages--;
}
static int has_wrprotected_page(struct kvm *kvm,
@@ -3233,6 +3235,13 @@
int level, npte, invlpg_counter, r, flooded = 0;
bool remote_flush, local_flush, zap_page;
+ /*
+ * If we don't have indirect shadow pages, it means no page is
+ * write-protected, so we can exit simply.
+ */
+ if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
+ return;
+
zap_page = remote_flush = local_flush = false;
offset = offset_in_page(gpa);
