[06/15] KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks
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Message ID 20210302184540.2829328-7-seanjc@google.com
State New, archived
Headers show
Series
  • KVM: x86/mmu: Lots of bug fixes
Related show

Commit Message

Sean Christopherson March 2, 2021, 6:45 p.m. UTC
Exempt NULL PAE roots from the check to detect leaks, since
kvm_mmu_free_roots() doesn't set them back to INVALID_PAGE.  Stop hiding
the WARNs to detect PAE root leaks behind MMU_WARN_ON, the hidden WARNs
obviously didn't do their job given the hilarious number of bugs that
could lead to PAE roots being leaked, not to mention the above false
positive.

Opportunistically delete a warning on root_hpa being valid, there's
nothing special about 4/5-level shadow pages that warrants a WARN.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Patch
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diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index aa20e8d32197..3ef7fb2a9878 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3244,7 +3244,8 @@  static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 		vcpu->arch.mmu->root_hpa = root;
 	} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
 		for (i = 0; i < 4; ++i) {
-			MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
+			WARN_ON_ONCE(vcpu->arch.mmu->pae_root[i] &&
+				     VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
 
 			root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT),
 					      i << 30, PT32_ROOT_LEVEL, true);
@@ -3289,8 +3290,6 @@  static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	 * write-protect the guests page table root.
 	 */
 	if (vcpu->arch.mmu->root_level >= PT64_ROOT_4LEVEL) {
-		MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->root_hpa));
-
 		root = mmu_alloc_root(vcpu, root_gfn, 0,
 				      vcpu->arch.mmu->shadow_root_level, false);
 		vcpu->arch.mmu->root_hpa = root;
@@ -3339,7 +3338,8 @@  static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	}
 
 	for (i = 0; i < 4; ++i) {
-		MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
+		WARN_ON_ONCE(vcpu->arch.mmu->pae_root[i] &&
+			     VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
 
 		if (vcpu->arch.mmu->root_level == PT32E_ROOT_LEVEL) {
 			if (!(pdptrs[i] & PT_PRESENT_MASK)) {