KVM: MMU: don't write-protect if have new mapping to unsync page (e02aa901) · Commits · 戴 / test

Two cases maybe happen in kvm_mmu_get_page() function: - one case is, the goal sp is already in cache, if the sp is unsync, we only need update it to assure this mapping is valid, but not mark it sync and not write-protect sp->gfn since it not broke unsync rule(one shadow page for a gfn) - another case is, the goal sp not existed, we need create a new sp for gfn, i.e, gfn (may)has another shadow page, to keep unsync rule, we should sync(mark sync and write-protect) gfn's unsync shadow page. After enabling multiple unsync shadows, we sync those shadow pages only when the new sp not allow to become unsync(also for the unsyc rule, the new rule is: allow all pte page become unsync) Signed-off-by:

Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Signed-off-by:

Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

+14 −4

Original line number	Diff line number	Diff line
		@@ -1337,7 +1337,7 @@ static struct kvm_mmu_page kvm_mmu_get_page(struct kvm_vcpu vcpu,
		unsigned index;
		unsigned quadrant;
		struct hlist_head *bucket;
		struct kvm_mmu_page *sp;
		struct kvm_mmu_page sp, unsync_sp = NULL;
		struct hlist_node node, tmp;

		role = vcpu->arch.mmu.base_role;
		@@ -1356,20 +1356,30 @@ static struct kvm_mmu_page kvm_mmu_get_page(struct kvm_vcpu vcpu,
		hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
		if (sp->gfn == gfn) {
		if (sp->unsync)
		if (kvm_sync_page(vcpu, sp))
		continue;
		unsync_sp = sp;

		if (sp->role.word != role.word)
		continue;

		if (!direct && unsync_sp &&
		kvm_sync_page_transient(vcpu, unsync_sp)) {
		unsync_sp = NULL;
		break;
		}

		mmu_page_add_parent_pte(vcpu, sp, parent_pte);
		if (sp->unsync_children) {
		set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
		kvm_mmu_mark_parents_unsync(sp);
		}
		} else if (sp->unsync)
		kvm_mmu_mark_parents_unsync(sp);

		trace_kvm_mmu_get_page(sp, false);
		return sp;
		}
		if (!direct && unsync_sp)
		kvm_sync_page(vcpu, unsync_sp);

		++vcpu->kvm->stat.mmu_cache_miss;
		sp = kvm_mmu_alloc_page(vcpu, parent_pte);
		if (!sp)

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