KVM: MMU: rewrite audit_mappings_page() function

There is a bugs in this function, we call gfn_to_pfn() and kvm_mmu_gva_to_gpa_read() in
atomic context(kvm_mmu_audit() is called under the spinlock(mmu_lock)'s protection).

This patch fix it by:
- introduce gfn_to_pfn_atomic instead of gfn_to_pfn
- get the mapping gfn from kvm_mmu_page_get_gfn()

And it adds 'notrap' ptes check in unsync/direct sps

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -3487,15 +3487,6 @@ EXPORT_SYMBOL_GPL(kvm_mmu_get_spte_hierarchy);
 
 static const char *audit_msg;
 
-static gva_t canonicalize(gva_t gva)
-{
-#ifdef CONFIG_X86_64
-	gva = (long long)(gva << 16) >> 16;
-#endif
-	return gva;
-}
-
-
 typedef void (*inspect_spte_fn) (struct kvm *kvm, u64 *sptep);
 
 static void __mmu_spte_walk(struct kvm *kvm, struct kvm_mmu_page *sp,
@@ -3550,39 +3541,53 @@ static void audit_mappings_page(struct kvm_vcpu *vcpu, u64 page_pte,
 	gva_t va_delta = 1ul << (PAGE_SHIFT + 9 * (level - 1));
 
 	for (i = 0; i < PT64_ENT_PER_PAGE; ++i, va += va_delta) {
-		u64 ent = pt[i];
+		u64 *sptep = pt + i;
+		struct kvm_mmu_page *sp;
+		gfn_t gfn;
+		pfn_t pfn;
+		hpa_t hpa;
 
-		if (ent == shadow_trap_nonpresent_pte)
-			continue;
+		sp = page_header(__pa(sptep));
 
-		va = canonicalize(va);
-		if (is_shadow_present_pte(ent) && !is_last_spte(ent, level))
-			audit_mappings_page(vcpu, ent, va, level - 1);
-		else {
-			gpa_t gpa = kvm_mmu_gva_to_gpa_read(vcpu, va, NULL);
-			gfn_t gfn = gpa >> PAGE_SHIFT;
-			pfn_t pfn = gfn_to_pfn(vcpu->kvm, gfn);
-			hpa_t hpa = (hpa_t)pfn << PAGE_SHIFT;
-
-			if (is_error_pfn(pfn)) {
-				kvm_release_pfn_clean(pfn);
-				continue;
+		if (sp->unsync) {
+			if (level != PT_PAGE_TABLE_LEVEL) {
+				printk(KERN_ERR "audit: (%s) error: unsync sp: %p level = %d\n",
+						audit_msg, sp, level);
+				return;
 			}
 
-			if (is_shadow_present_pte(ent)
-			    && (ent & PT64_BASE_ADDR_MASK) != hpa)
-				printk(KERN_ERR "xx audit error: (%s) levels %d"
-				       " gva %lx gpa %llx hpa %llx ent %llx %d\n",
-				       audit_msg, vcpu->arch.mmu.root_level,
-				       va, gpa, hpa, ent,
-				       is_shadow_present_pte(ent));
-			else if (ent == shadow_notrap_nonpresent_pte
-				 && !is_error_hpa(hpa))
-				printk(KERN_ERR "audit: (%s) notrap shadow,"
-				       " valid guest gva %lx\n", audit_msg, va);
-			kvm_release_pfn_clean(pfn);
-
+			if (*sptep == shadow_notrap_nonpresent_pte) {
+				printk(KERN_ERR "audit: (%s) error: notrap spte in unsync sp: %p\n",
+						audit_msg, sp);
+				return;
+			}
 		}
+
+		if (sp->role.direct && *sptep == shadow_notrap_nonpresent_pte) {
+			printk(KERN_ERR "audit: (%s) error: notrap spte in direct sp: %p\n",
+					audit_msg, sp);
+			return;
+		}
+
+		if (!is_shadow_present_pte(*sptep) ||
+		      !is_last_spte(*sptep, level))
+			return;
+
+		gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt);
+		pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
+
+		if (is_error_pfn(pfn)) {
+			kvm_release_pfn_clean(pfn);
+			return;
+		}
+
+		hpa =  pfn << PAGE_SHIFT;
+
+		if ((*sptep & PT64_BASE_ADDR_MASK) != hpa)
+			printk(KERN_ERR "xx audit error: (%s) levels %d"
+					   " gva %lx pfn %llx hpa %llx ent %llxn",
+					   audit_msg, vcpu->arch.mmu.root_level,
+					   va, pfn, hpa, *sptep);
 	}
 }
 

include/linux/kvm_host.h

@@ -300,6 +300,7 @@ void kvm_set_page_dirty(struct page *page);
 void kvm_set_page_accessed(struct page *page);
 
 pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr);
+pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
 			 struct kvm_memory_slot *slot, gfn_t gfn);

virt/kvm/kvm_main.c

@@ -999,7 +999,7 @@ pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(hva_to_pfn_atomic);
 
-pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic)
 {
 	unsigned long addr;
 
@@ -1009,7 +1009,18 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
 		return page_to_pfn(bad_page);
 	}
 
-	return hva_to_pfn(kvm, addr, false);
+	return hva_to_pfn(kvm, addr, atomic);
+}
+
+pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
+{
+	return __gfn_to_pfn(kvm, gfn, true);
+}
+EXPORT_SYMBOL_GPL(gfn_to_pfn_atomic);
+
+pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+{
+	return __gfn_to_pfn(kvm, gfn, false);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn);