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Commit 4e103134 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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KVM: x86/mmu: Zap only the relevant pages when removing a memslot 



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@gmail.com>
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a2113634

arch/x86/kvm/mmu.c

+32 −1
Original line number Diff line number Diff line
@@ -5622,7 +5622,38 @@ 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)