From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sasha Levin <sashal@kernel.org>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org
Subject: [PATCH MANUALSEL 5.16 4/8] KVM: nVMX: WARN on any attempt to allocate shadow VMCS for vmcs02
Date: Wed, 9 Feb 2022 13:56:30 -0500 [thread overview]
Message-ID: <20220209185635.48730-4-sashal@kernel.org> (raw)
In-Reply-To: <20220209185635.48730-1-sashal@kernel.org>
From: Sean Christopherson <seanjc@google.com>
[ Upstream commit d6e656cd266cdcc95abd372c7faef05bee271d1a ]
WARN if KVM attempts to allocate a shadow VMCS for vmcs02. KVM emulates
VMCS shadowing but doesn't virtualize it, i.e. KVM should never allocate
a "real" shadow VMCS for L2.
The previous code WARNed but continued anyway with the allocation,
presumably in an attempt to avoid NULL pointer dereference.
However, alloc_vmcs (and hence alloc_shadow_vmcs) can fail, and
indeed the sole caller does:
if (enable_shadow_vmcs && !alloc_shadow_vmcs(vcpu))
goto out_shadow_vmcs;
which makes it not a useful attempt.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220125220527.2093146-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/vmx/nested.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c605c2c01394b..9cd68e1fcf602 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4827,18 +4827,20 @@ static struct vmcs *alloc_shadow_vmcs(struct kvm_vcpu *vcpu)
struct loaded_vmcs *loaded_vmcs = vmx->loaded_vmcs;
/*
- * We should allocate a shadow vmcs for vmcs01 only when L1
- * executes VMXON and free it when L1 executes VMXOFF.
- * As it is invalid to execute VMXON twice, we shouldn't reach
- * here when vmcs01 already have an allocated shadow vmcs.
+ * KVM allocates a shadow VMCS only when L1 executes VMXON and frees it
+ * when L1 executes VMXOFF or the vCPU is forced out of nested
+ * operation. VMXON faults if the CPU is already post-VMXON, so it
+ * should be impossible to already have an allocated shadow VMCS. KVM
+ * doesn't support virtualization of VMCS shadowing, so vmcs01 should
+ * always be the loaded VMCS.
*/
- WARN_ON(loaded_vmcs == &vmx->vmcs01 && loaded_vmcs->shadow_vmcs);
+ if (WARN_ON(loaded_vmcs != &vmx->vmcs01 || loaded_vmcs->shadow_vmcs))
+ return loaded_vmcs->shadow_vmcs;
+
+ loaded_vmcs->shadow_vmcs = alloc_vmcs(true);
+ if (loaded_vmcs->shadow_vmcs)
+ vmcs_clear(loaded_vmcs->shadow_vmcs);
- if (!loaded_vmcs->shadow_vmcs) {
- loaded_vmcs->shadow_vmcs = alloc_vmcs(true);
- if (loaded_vmcs->shadow_vmcs)
- vmcs_clear(loaded_vmcs->shadow_vmcs);
- }
return loaded_vmcs->shadow_vmcs;
}
--
2.34.1
next prev parent reply other threads:[~2022-02-09 18:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 18:56 [PATCH MANUALSEL 5.16 1/8] KVM: eventfd: Fix false positive RCU usage warning Sasha Levin
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 2/8] KVM: nVMX: eVMCS: Filter out VM_EXIT_SAVE_VMX_PREEMPTION_TIMER Sasha Levin
2022-02-10 16:42 ` Paolo Bonzini
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 3/8] KVM: nVMX: Also filter MSR_IA32_VMX_TRUE_PINBASED_CTLS when eVMCS Sasha Levin
2022-02-10 16:42 ` Paolo Bonzini
2022-02-09 18:56 ` Sasha Levin [this message]
2022-02-10 16:33 ` [PATCH MANUALSEL 5.16 4/8] KVM: nVMX: WARN on any attempt to allocate shadow VMCS for vmcs02 Paolo Bonzini
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 5/8] KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode Sasha Levin
2022-02-10 16:33 ` Paolo Bonzini
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 6/8] KVM: SVM: Explicitly require DECODEASSISTS to enable SEV support Sasha Levin
2022-02-10 16:33 ` Paolo Bonzini
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 7/8] KVM: VMX: Set vmcs.PENDING_DBG.BS on #DB in STI/MOVSS blocking shadow Sasha Levin
2022-02-10 16:42 ` Paolo Bonzini
2022-02-09 18:56 ` [PATCH MANUALSEL 5.16 8/8] KVM: x86: Report deprecated x87 features in supported CPUID Sasha Levin
2022-02-10 16:42 ` Paolo Bonzini
2022-02-10 16:41 ` [PATCH MANUALSEL 5.16 1/8] KVM: eventfd: Fix false positive RCU usage warning Paolo Bonzini
2022-02-12 22:20 ` Sasha Levin
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