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Commit a4ee1ca4 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Avi Kivity
Browse files

KVM: MMU: delay flush all tlbs on sync_page path 



Quote from Avi:
| I don't think we need to flush immediately; set a "tlb dirty" bit somewhere
| that is cleareded when we flush the tlb.  kvm_mmu_notifier_invalidate_page()
| can consult the bit and force a flush if set.

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 407c61c6

arch/x86/kvm/paging_tmpl.h

+10 −2
Original line number Diff line number Diff line
@@ -746,6 +746,14 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu, 
 * Using the cached information from sp->gfns is safe because:

 * - The spte has a reference to the struct page, so the pfn for a given gfn

 *   can't change unless all sptes pointing to it are nuked first.

 *

 * Note:

 *   We should flush all tlbs if spte is dropped even though guest is

 *   responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page

 *   and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't

 *   used by guest then tlbs are not flushed, so guest is allowed to access the

 *   freed pages.

 *   And we increase kvm->tlbs_dirty to delay tlbs flush in this case.

 */

static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)

{
@@ -781,14 +789,14 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
		gfn = gpte_to_gfn(gpte);



		if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {

			kvm_flush_remote_tlbs(vcpu->kvm);

			vcpu->kvm->tlbs_dirty++;

			continue;

		}



		if (gfn != sp->gfns[i]) {

			drop_spte(vcpu->kvm, &sp->spt[i],

				      shadow_trap_nonpresent_pte);

			kvm_flush_remote_tlbs(vcpu->kvm);

			vcpu->kvm->tlbs_dirty++;

			continue;

		}

include/linux/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -254,6 +254,7 @@ struct kvm { 
	struct mmu_notifier mmu_notifier;

	unsigned long mmu_notifier_seq;

	long mmu_notifier_count;

	long tlbs_dirty;

#endif

};
@@ -382,6 +383,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu); 
void kvm_resched(struct kvm_vcpu *vcpu);

void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);

void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);



void kvm_flush_remote_tlbs(struct kvm *kvm);

void kvm_reload_remote_mmus(struct kvm *kvm);

virt/kvm/kvm_main.c

+6 −1
Original line number Diff line number Diff line
@@ -168,8 +168,12 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) 


void kvm_flush_remote_tlbs(struct kvm *kvm)

{

	int dirty_count = kvm->tlbs_dirty;



	smp_mb();

	if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))

		++kvm->stat.remote_tlb_flush;

	cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);

}



void kvm_reload_remote_mmus(struct kvm *kvm)
@@ -249,7 +253,7 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn, 
	idx = srcu_read_lock(&kvm->srcu);

	spin_lock(&kvm->mmu_lock);

	kvm->mmu_notifier_seq++;

	need_tlb_flush = kvm_unmap_hva(kvm, address);

	need_tlb_flush = kvm_unmap_hva(kvm, address) | kvm->tlbs_dirty;

	spin_unlock(&kvm->mmu_lock);

	srcu_read_unlock(&kvm->srcu, idx);
@@ -293,6 +297,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, 
	kvm->mmu_notifier_count++;

	for (; start < end; start += PAGE_SIZE)

		need_tlb_flush |= kvm_unmap_hva(kvm, start);

	need_tlb_flush |= kvm->tlbs_dirty;

	spin_unlock(&kvm->mmu_lock);

	srcu_read_unlock(&kvm->srcu, idx);