[PATCH] KVM: MMU: Bail out immediately if there is no available mmu page

[Wanpeng Li]

From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

Bailing out immediately if there is no available mmu page to alloc.

Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
 arch/x86/kvm/mmu.c         | 36 +++++++++++++++++++++++++++---------
 arch/x86/kvm/paging_tmpl.h |  3 ++-
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 849312d..e7d1bb1 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3257,7 +3257,7 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
 
 static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
 			 gva_t gva, kvm_pfn_t *pfn, bool write, bool *writable);
-static void make_mmu_pages_available(struct kvm_vcpu *vcpu);
+static int make_mmu_pages_available(struct kvm_vcpu *vcpu);
 
 static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
 			 gfn_t gfn, bool prefault)
@@ -3297,7 +3297,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
 	spin_lock(&vcpu->kvm->mmu_lock);
 	if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
 		goto out_unlock;
-	make_mmu_pages_available(vcpu);
+	if (make_mmu_pages_available(vcpu) < 0)
+		goto out_unlock;
 	if (likely(!force_pt_level))
 		transparent_hugepage_adjust(vcpu, &gfn, &pfn, &level);
 	r = __direct_map(vcpu, write, map_writable, level, gfn, pfn, prefault);
@@ -3376,7 +3377,10 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 
 	if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
 		spin_lock(&vcpu->kvm->mmu_lock);
-		make_mmu_pages_available(vcpu);
+		if(make_mmu_pages_available(vcpu) < 0) {
+			spin_unlock(&vcpu->kvm->mmu_lock);
+			return 1;
+		}
 		sp = kvm_mmu_get_page(vcpu, 0, 0, PT64_ROOT_LEVEL, 1, ACC_ALL);
 		++sp->root_count;
 		spin_unlock(&vcpu->kvm->mmu_lock);
@@ -3387,7 +3391,10 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 
 			MMU_WARN_ON(VALID_PAGE(root));
 			spin_lock(&vcpu->kvm->mmu_lock);
-			make_mmu_pages_available(vcpu);
+			if (make_mmu_pages_available(vcpu) < 0) {
+				spin_unlock(&vcpu->kvm->mmu_lock);
+				return 1;
+			}
 			sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT),
 					i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL);
 			root = __pa(sp->spt);
@@ -3424,7 +3431,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 		MMU_WARN_ON(VALID_PAGE(root));
 
 		spin_lock(&vcpu->kvm->mmu_lock);
-		make_mmu_pages_available(vcpu);
+		if (make_mmu_pages_available(vcpu) < 0) {
+			spin_unlock(&vcpu->kvm->mmu_lock);
+			return 1;
+		}
 		sp = kvm_mmu_get_page(vcpu, root_gfn, 0, PT64_ROOT_LEVEL,
 				      0, ACC_ALL);
 		root = __pa(sp->spt);
@@ -3458,7 +3468,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 				return 1;
 		}
 		spin_lock(&vcpu->kvm->mmu_lock);
-		make_mmu_pages_available(vcpu);
+		if (make_mmu_pages_available(vcpu) < 0) {
+			spin_unlock(&vcpu->kvm->mmu_lock);
+			return 1;
+		}
 		sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL,
 				      0, ACC_ALL);
 		root = __pa(sp->spt);
@@ -3869,7 +3882,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 	spin_lock(&vcpu->kvm->mmu_lock);
 	if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
 		goto out_unlock;
-	make_mmu_pages_available(vcpu);
+	if (make_mmu_pages_available(vcpu) < 0)
+		goto out_unlock;
 	if (likely(!force_pt_level))
 		transparent_hugepage_adjust(vcpu, &gfn, &pfn, &level);
 	r = __direct_map(vcpu, write, map_writable, level, gfn, pfn, prefault);
@@ -4788,12 +4802,12 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page_virt);
 
-static void make_mmu_pages_available(struct kvm_vcpu *vcpu)
+static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
 {
 	LIST_HEAD(invalid_list);
 
 	if (likely(kvm_mmu_available_pages(vcpu->kvm) >= KVM_MIN_FREE_MMU_PAGES))
-		return;
+		return 0;
 
 	while (kvm_mmu_available_pages(vcpu->kvm) < KVM_REFILL_PAGES) {
 		if (!prepare_zap_oldest_mmu_page(vcpu->kvm, &invalid_list))
@@ -4802,6 +4816,10 @@ static void make_mmu_pages_available(struct kvm_vcpu *vcpu)
 		++vcpu->kvm->stat.mmu_recycled;
 	}
 	kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
+
+	if (!kvm_mmu_available_pages(vcpu->kvm))
+		return -ENOSPC;
+	return 0;
 }
 
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index b0454c7..3bb90ce 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -819,7 +819,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 		goto out_unlock;
 
 	kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
-	make_mmu_pages_available(vcpu);
+	if (make_mmu_pages_available(vcpu) < 0)
+		goto out_unlock;
 	if (!force_pt_level)
 		transparent_hugepage_adjust(vcpu, &walker.gfn, &pfn, &level);
 	r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
-- 
2.7.4