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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 v2 08/17] KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks
Date: Thu,  4 Mar 2021 17:10:52 -0800	[thread overview]
Message-ID: <20210305011101.3597423-9-seanjc@google.com> (raw)
In-Reply-To: <20210305011101.3597423-1-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 | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 9fc2b46f8541..b82c1b0d6d6e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3250,7 +3250,8 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 		mmu->root_hpa = root;
 	} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
 		for (i = 0; i < 4; ++i) {
-			MMU_WARN_ON(VALID_PAGE(mmu->pae_root[i]));
+			WARN_ON_ONCE(mmu->pae_root[i] &&
+				     VALID_PAGE(mmu->pae_root[i]));
 
 			root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT),
 					      i << 30, PT32_ROOT_LEVEL, true);
@@ -3296,8 +3297,6 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	 * write-protect the guests page table root.
 	 */
 	if (mmu->root_level >= PT64_ROOT_4LEVEL) {
-		MMU_WARN_ON(VALID_PAGE(mmu->root_hpa));
-
 		root = mmu_alloc_root(vcpu, root_gfn, 0,
 				      mmu->shadow_root_level, false);
 		mmu->root_hpa = root;
@@ -3317,7 +3316,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	}
 
 	for (i = 0; i < 4; ++i) {
-		MMU_WARN_ON(VALID_PAGE(mmu->pae_root[i]));
+		WARN_ON_ONCE(mmu->pae_root[i] && VALID_PAGE(mmu->pae_root[i]));
 
 		if (mmu->root_level == PT32E_ROOT_LEVEL) {
 			if (!(pdptrs[i] & PT_PRESENT_MASK)) {
-- 
2.30.1.766.gb4fecdf3b7-goog


  parent reply	other threads:[~2021-03-05  1:11 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-05  1:10 [PATCH v2 00/17] KVM: x86/mmu: Lots of bug fixes Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 01/17] KVM: nSVM: Set the shadow root level to the TDP level for nested NPT Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 02/17] KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 03/17] KVM: x86/mmu: Capture 'mmu' in a local variable when allocating roots Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 04/17] KVM: x86/mmu: Allocate the lm_root before allocating PAE roots Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 05/17] KVM: x86/mmu: Allocate pae_root and lm_root pages in dedicated helper Sean Christopherson
2021-03-05 17:34   ` Paolo Bonzini
2021-03-05  1:10 ` [PATCH v2 06/17] KVM: x86/mmu: Ensure MMU pages are available when allocating roots Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 07/17] KVM: x86/mmu: Check PDPTRs before allocating PAE roots Sean Christopherson
2021-04-08 11:15   ` Wanpeng Li
2021-04-08 12:09     ` Paolo Bonzini
2021-04-08 15:48       ` Sean Christopherson
2021-04-08 15:57         ` Paolo Bonzini
2021-04-08 16:27           ` Sean Christopherson
2021-04-08 16:30             ` Paolo Bonzini
2021-03-05  1:10 ` Sean Christopherson [this message]
2021-03-05  1:10 ` [PATCH v2 09/17] KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE root Sean Christopherson
2021-03-05 17:52   ` Paolo Bonzini
2021-03-05 18:22     ` Sean Christopherson
2021-03-05 18:23       ` Paolo Bonzini
2021-03-05  1:10 ` [PATCH v2 10/17] KVM: x86/mmu: Set the C-bit in the PDPTRs and LM pseudo-PDPTRs Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 11/17] KVM: x86/mmu: Mark the PAE roots as decrypted for shadow paging Sean Christopherson
2021-03-05 17:44   ` Paolo Bonzini
2021-03-05 18:02     ` Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 12/17] KVM: SVM: Don't strip the C-bit from CR2 on #PF interception Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 13/17] KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 14/17] KVM: x86: Defer the MMU unload to the normal path on an global INVPCID Sean Christopherson
2021-03-05  1:10 ` [PATCH v2 15/17] KVM: x86/mmu: Unexport MMU load/unload functions Sean Christopherson
2021-03-05  1:11 ` [PATCH v2 16/17] KVM: x86/mmu: Sync roots after MMU load iff load as successful Sean Christopherson
2021-03-05  1:11 ` [PATCH v2 17/17] KVM: x86/mmu: WARN on NULL pae_root or lm_root, or bad shadow root level Sean Christopherson
2021-03-05 17:53 ` [PATCH v2 00/17] KVM: x86/mmu: Lots of bug fixes Paolo Bonzini

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