Commit 8d5678a7 authored by Hou Wenlong's avatar Hou Wenlong Committed by Paolo Bonzini
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KVM: x86/mmu: Don't rebuild page when the page is synced and no tlb flushing is required 



Before Commit c3e5e415 ("KVM: X86: Change kvm_sync_page()
to return true when remote flush is needed"), the return value
of kvm_sync_page() indicates whether the page is synced, and
kvm_mmu_get_page() would rebuild page when the sync fails.
But now, kvm_sync_page() returns false when the page is
synced and no tlb flushing is required, which leads to
rebuild page in kvm_mmu_get_page(). So return the return
value of mmu->sync_page() directly and check it in
kvm_mmu_get_page(). If the sync fails, the page will be
zapped and the invalid_list is not empty, so set flush as
true is accepted in mmu_sync_children().

Cc: stable@vger.kernel.org
Fixes: c3e5e415 ("KVM: X86: Change kvm_sync_page() to return true when remote flush is needed")
Signed-off-by: default avatarHou Wenlong <houwenlong.hwl@antgroup.com>
Acked-by: default avatarLai Jiangshan <jiangshanlai@gmail.com>
Message-Id: <0dabeeb789f57b0d793f85d073893063e692032d.1647336064.git.houwenlong.hwl@antgroup.com>
[mmu_sync_children should not flush if the page is zapped. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 945024d7

arch/x86/kvm/mmu/mmu.c

+9 −9
Original line number Diff line number Diff line
@@ -1866,17 +1866,14 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, 
	  &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)])	\

		if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else



static bool kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,

static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,

			 struct list_head *invalid_list)

{

	int ret = vcpu->arch.mmu->sync_page(vcpu, sp);



	if (ret < 0) {

	if (ret < 0)

		kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);

		return false;

	}



	return !!ret;

	return ret;

}



static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm,
@@ -1998,7 +1995,7 @@ static int mmu_sync_children(struct kvm_vcpu *vcpu, 


		for_each_sp(pages, sp, parents, i) {

			kvm_unlink_unsync_page(vcpu->kvm, sp);

			flush |= kvm_sync_page(vcpu, sp, &invalid_list);

			flush |= kvm_sync_page(vcpu, sp, &invalid_list) > 0;

			mmu_pages_clear_parents(&parents);

		}

		if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {
@@ -2039,6 +2036,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
	struct hlist_head *sp_list;

	unsigned quadrant;

	struct kvm_mmu_page *sp;

	int ret;

	int collisions = 0;

	LIST_HEAD(invalid_list);
@@ -2091,10 +2089,12 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
			 * If the sync fails, the page is zapped.  If so, break

			 * in order to rebuild it.

			 */

			if (!kvm_sync_page(vcpu, sp, &invalid_list))

			ret = kvm_sync_page(vcpu, sp, &invalid_list);

			if (ret < 0)

				break;



			WARN_ON(!list_empty(&invalid_list));

			if (ret > 0)

				kvm_flush_remote_tlbs(vcpu->kvm);

		}