Modify kvm_mmu_invalidate_zap_pages_in_memslot(), a.k.a. the x86 MMU's
handler for kvm_arch_flush_shadow_memslot(), to zap only the pages/PTEs
that actually belong to the memslot being removed. This improves
performance, especially why the deleted memslot has only a few shadow
entries, or even no entries. E.g. a microbenchmark to access regular
memory while concurrently reading PCI ROM to trigger memslot deletion
showed a 5% improvement in throughput.
Cc: Xiao Guangrong <guangrong.xiao@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/mmu.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b6f362a988fd..ba96bf9cf706 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5619,7 +5619,38 @@ static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot,
struct kvm_page_track_notifier_node *node)
{
- kvm_mmu_invalidate_zap_all_pages(kvm);
+ struct kvm_mmu_page *sp;
+ LIST_HEAD(invalid_list);
+ unsigned long i;
+ bool flush;
+ gfn_t gfn;
+
+ spin_lock(&kvm->mmu_lock);
+
+ if (list_empty(&kvm->arch.active_mmu_pages))
+ goto out_unlock;
+
+ flush = slot_handle_all_level(kvm, slot, kvm_zap_rmapp, false);
+
+ for (i = 0; i < slot->npages; i++) {
+ gfn = slot->base_gfn + i;
+
+ for_each_valid_sp(kvm, sp, gfn) {
+ if (sp->gfn != gfn)
+ continue;
+
+ kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
+ }
+ if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
+ kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
+ flush = false;
+ cond_resched_lock(&kvm->mmu_lock);
+ }
+ }
+ kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
+
+out_unlock:
+ spin_unlock(&kvm->mmu_lock);
}
void kvm_mmu_init_vm(struct kvm *kvm)
--
2.20.1
