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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: [PATCH 06/15] KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks
Date: Tue,  2 Mar 2021 10:45:31 -0800	[thread overview]
Message-ID: <20210302184540.2829328-7-seanjc@google.com> (raw)
In-Reply-To: <20210302184540.2829328-1-seanjc@google.com>

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(-)

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)) {
-- 
2.30.1.766.gb4fecdf3b7-goog


  parent reply	other threads:[~2021-03-02 21:50 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-02 18:45 [PATCH 00/15] KVM: x86/mmu: Lots of bug fixes Sean Christopherson
2021-03-02 18:45 ` [PATCH 01/15] KVM: nSVM: Set the shadow root level to the TDP level for nested NPT Sean Christopherson
2021-03-02 18:45 ` [PATCH 02/15] KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit Sean Christopherson
2021-03-03 17:28   ` Ben Gardon
2021-03-02 18:45 ` [PATCH 03/15] KVM: x86/mmu: Ensure MMU pages are available when allocating roots Sean Christopherson
2021-03-03  0:21   ` Ben Gardon
2021-03-03 16:46     ` Sean Christopherson
2021-03-02 18:45 ` [PATCH 04/15] KVM: x86/mmu: Allocate the lm_root before allocating PAE roots Sean Christopherson
2021-03-02 18:45 ` [PATCH 05/15] KVM: x86/mmu: Check PDPTRs " Sean Christopherson
2021-03-02 18:45 ` Sean Christopherson [this message]
2021-03-02 18:45 ` [PATCH 07/15] KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE root Sean Christopherson
2021-03-02 18:45 ` [PATCH 08/15] KVM: x86/mmu: Set the C-bit in the PDPTRs and LM pseudo-PDPTRs Sean Christopherson
2021-03-02 18:45 ` [PATCH 09/15] KVM: x86/mmu: Mark the PAE roots as decrypted for shadow paging Sean Christopherson
2021-03-02 18:45 ` [PATCH 10/15] KVM: SVM: Don't strip the C-bit from CR2 on #PF interception Sean Christopherson
2021-03-02 18:45 ` [PATCH 11/15] KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch Sean Christopherson
2021-03-02 18:45 ` [PATCH 12/15] KVM: x86: Defer the MMU unload to the normal path on an global INVPCID Sean Christopherson
2021-03-02 18:45 ` [PATCH 13/15] KVM: x86/mmu: Unexport MMU load/unload functions Sean Christopherson
2021-03-02 18:45 ` [PATCH 14/15] KVM: x86/mmu: Sync roots after MMU load iff load as successful Sean Christopherson
2021-03-02 18:45 ` [PATCH 15/15] KVM: x86/mmu: WARN on NULL pae_root and bad shadow root level Sean Christopherson

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