[patch 1/4] KVM: MMU audit: update count_writable_mappings / count_rmaps

Marcelo Tosatti
2009-06-09T13:15:55Z

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Under testing, count_writable_mappings returns a value that is 2 integers
larger than what count_rmaps returns.

Suspicion is that either of the two functions is counting a duplicate (either
positively or negatively).

Modifying check_writable_mappings_rmap to check for rmap existance on
all present MMU pages fails to trigger an error, which should keep Avi
happy.

Also introduce mmu_spte_walk to invoke a callback on all present sptes visible
to the current vcpu, might be useful in the future.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm/arch/x86/kvm/mmu.c
===================================================================
--- kvm.orig/arch/x86/kvm/mmu.c
+++ kvm/arch/x86/kvm/mmu.c
@@ -3020,6 +3020,55 @@ static gva_t canonicalize(gva_t gva)
return gva;
}

+
+typedef void (*inspect_spte_fn) (struct kvm *kvm, struct kvm_mmu_page *sp,
+ u64 *sptep);
+
+static void __mmu_spte_walk(struct kvm *kvm, struct kvm_mmu_page *sp,
+ inspect_spte_fn fn)
+{
+ int i;
+
+ for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+ u64 ent = sp->spt[i];
+
+ if (is_shadow_present_pte(ent)) {
+ if (sp->role.level > 1 && !is_large_pte(ent)) {
+ struct kvm_mmu_page *child;
+ child = page_header(ent & PT64_BASE_ADDR_MASK);
+ __mmu_spte_walk(kvm, child, fn);
+ }
+ if (sp->role.level == 1)
+ fn(kvm, sp, &sp->spt[i]);
+ }
+ }
+}
+
+static void mmu_spte_walk(struct kvm_vcpu *vcpu, inspect_spte_fn fn)
+{
+ int i;
+ struct kvm_mmu_page *sp;
+
+ if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
+ return;
+ if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
+ hpa_t root = vcpu->arch.mmu.root_hpa;
+ sp = page_header(root);
+ __mmu_spte_walk(vcpu->kvm, sp, fn);
+ return;
+ }
+ for (i = 0; i < 4; ++i) {
+ hpa_t root = vcpu->arch.mmu.pae_root[i];
+
+ if (root && VALID_PAGE(root)) {
+ root &= PT64_BASE_ADDR_MASK;
+ sp = page_header(root);
+ __mmu_spte_walk(vcpu->kvm, sp, fn);
+ }
+ }
+ return;
+}
+
static void audit_mappings_page(struct kvm_vcpu *vcpu, u64 page_pte,
gva_t va, int level)
{
@@ -3112,9 +3161,43 @@ static int count_rmaps(struct kvm_vcpu *
return nmaps;
}

-static int count_writable_mappings(struct kvm_vcpu *vcpu)
+void inspect_spte_has_rmap(struct kvm *kvm, struct kvm_mmu_page *sp, u64 *sptep)
+{
+ unsigned long *rmapp;
+ struct kvm_mmu_page *rev_sp;
+ gfn_t gfn;
+
+ if (*sptep & PT_WRITABLE_MASK) {
+ rev_sp = page_header(__pa(sptep));
+ gfn = rev_sp->gfns[sptep - rev_sp->spt];
+
+ if (!gfn_to_memslot(kvm, gfn)) {
+ printk(KERN_ERR "%s: no memslot for gfn %ld\n",
+ audit_msg, gfn);
+ printk(KERN_ERR "%s: index %ld of sp (gfn=%lx)\n",
+ audit_msg, sptep - rev_sp->spt,
+ rev_sp->gfn);
+ dump_stack();
+ return;
+ }
+
+ rmapp = gfn_to_rmap(kvm, rev_sp->gfns[sptep - rev_sp->spt], 0);
+ if (!*rmapp) {
+ printk(KERN_ERR "%s: no rmap for writable spte %llx\n",
+ audit_msg, *sptep);
+ dump_stack();
+ }
+ }
+
+}
+
+void audit_writable_sptes_have_rmaps(struct kvm_vcpu *vcpu)
+{
+ mmu_spte_walk(vcpu, inspect_spte_has_rmap);
+}
+
+static void check_writable_mappings_rmap(struct kvm_vcpu *vcpu)
{
- int nmaps = 0;
struct kvm_mmu_page *sp;
int i;

@@ -3131,20 +3214,16 @@ static int count_writable_mappings(struc
continue;
if (!(ent & PT_WRITABLE_MASK))
continue;
- ++nmaps;
+ inspect_spte_has_rmap(vcpu->kvm, sp, &pt[i]);
}
}
- return nmaps;
+ return;
}

static void audit_rmap(struct kvm_vcpu *vcpu)
{
- int n_rmap = count_rmaps(vcpu);
- int n_actual = count_writable_mappings(vcpu);
-
- if (n_rmap != n_actual)
- printk(KERN_ERR "%s: (%s) rmap %d actual %d\n",
- __func__, audit_msg, n_rmap, n_actual);
+ check_writable_mappings_rmap(vcpu);
+ count_rmaps(vcpu);
}

static void audit_write_protection(struct kvm_vcpu *vcpu)
@@ -3178,6 +3257,7 @@ static void kvm_mmu_audit(struct kvm_vcp
audit_rmap(vcpu);
audit_write_protection(vcpu);
audit_mappings(vcpu);
+ audit_writable_sptes_have_rmaps(vcpu);
dbg = olddbg;
}

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