Commit c3e5e415 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Paolo Bonzini
Browse files

KVM: X86: Change kvm_sync_page() to return true when remote flush is needed 



Currently kvm_sync_page() returns true when there is any present spte.
But the return value is ignored in the callers.

Changing kvm_sync_page() to return true when remote flush is needed and
changing mmu->sync_page() not to directly flush can combine and reduce
remote flush requests.

Signed-off-by: default avatarLai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210918005636.3675-7-jiangshanlai@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 06152b2d

arch/x86/kvm/mmu/mmu.c

+13 −8
Original line number Diff line number Diff line
@@ -1795,7 +1795,7 @@ static void mark_unsync(u64 *spte) 
static int nonpaging_sync_page(struct kvm_vcpu *vcpu,

			       struct kvm_mmu_page *sp)

{

	return 0;

	return -1;

}



#define KVM_PAGE_ARRAY_NR 16
@@ -1909,12 +1909,14 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, 
static bool kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,

			 struct list_head *invalid_list)

{

	if (vcpu->arch.mmu->sync_page(vcpu, sp) == 0) {

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



	if (ret < 0) {

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

		return false;

	}



	return true;

	return !!ret;

}



static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm,
@@ -2024,6 +2026,7 @@ static int mmu_sync_children(struct kvm_vcpu *vcpu, 
	struct mmu_page_path parents;

	struct kvm_mmu_pages pages;

	LIST_HEAD(invalid_list);

	bool flush = false;



	while (mmu_unsync_walk(parent, &pages)) {

		bool protected = false;
@@ -2033,25 +2036,27 @@ static int mmu_sync_children(struct kvm_vcpu *vcpu, 


		if (protected) {

			kvm_flush_remote_tlbs(vcpu->kvm);

			flush = false;

		}



		for_each_sp(pages, sp, parents, i) {

			kvm_unlink_unsync_page(vcpu->kvm, sp);

			kvm_sync_page(vcpu, sp, &invalid_list);

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

			mmu_pages_clear_parents(&parents);

		}

		if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {

			kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, false);

			kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);

			if (!can_yield) {

				kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);

				return -EINTR;

			}



			cond_resched_rwlock_write(&vcpu->kvm->mmu_lock);

			flush = false;

		}

	}



	kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, false);

	kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);

	return 0;

}
@@ -2135,6 +2140,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 
				break;



			WARN_ON(!list_empty(&invalid_list));

			kvm_flush_remote_tlbs(vcpu->kvm);

		}



		__clear_sp_write_flooding_count(sp);
@@ -4191,7 +4197,7 @@ static unsigned long get_cr3(struct kvm_vcpu *vcpu) 
}



static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,

			   unsigned int access, int *nr_present)

			   unsigned int access)

{

	if (unlikely(is_mmio_spte(*sptep))) {

		if (gfn != get_mmio_spte_gfn(*sptep)) {
@@ -4199,7 +4205,6 @@ static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn, 
			return true;

		}



		(*nr_present)++;

		mark_mmio_spte(vcpu, sptep, gfn, access);

		return true;

	}

arch/x86/kvm/mmu/paging_tmpl.h

+10 −11
Original line number Diff line number Diff line
@@ -1066,11 +1066,16 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gpa_t vaddr, 
 * 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.

 *

 * Returns

 * < 0: the sp should be zapped

 *   0: the sp is synced and no tlb flushing is required

 * > 0: the sp is synced and tlb flushing is required

 */

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

{

	union kvm_mmu_page_role mmu_role = vcpu->arch.mmu->mmu_role.base;

	int i, nr_present = 0;

	int i;

	bool host_writable;

	gpa_t first_pte_gpa;

	int set_spte_ret = 0;
@@ -1098,7 +1103,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
	 */

	if (WARN_ON_ONCE(sp->role.direct ||

			 (sp->role.word ^ mmu_role.word) & ~sync_role_ign.word))

		return 0;

		return -1;



	first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
@@ -1115,7 +1120,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 


		if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,

					       sizeof(pt_element_t)))

			return 0;

			return -1;



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

			set_spte_ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
@@ -1127,8 +1132,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
		pte_access &= FNAME(gpte_access)(gpte);

		FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);



		if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access,

		      &nr_present))

		if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access))

			continue;



		if (gfn != sp->gfns[i]) {
@@ -1137,8 +1141,6 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
			continue;

		}



		nr_present++;



		host_writable = sp->spt[i] & shadow_host_writable_mask;



		set_spte_ret |= set_spte(vcpu, &sp->spt[i],
@@ -1147,10 +1149,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
					 true, false, host_writable);

	}



	if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)

		kvm_flush_remote_tlbs(vcpu->kvm);



	return nr_present;

	return set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH;

}



#undef pt_element_t