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authorSean Christopherson <seanjc@google.com>2022-01-25 22:05:27 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2022-01-26 12:15:04 -0500
commitd6e656cd266cdcc95abd372c7faef05bee271d1a (patch)
treebaa1358ffb64afbc2e1904f3e96886b861041166 /arch
parent4cf3d3ebe8794c449af3e0e8c1d790c97e461d20 (diff)
downloadlinux-d6e656cd266cdcc95abd372c7faef05bee271d1a.tar.bz2
KVM: nVMX: WARN on any attempt to allocate shadow VMCS for vmcs02
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/vmx/nested.c22
1 files changed, 12 insertions, 10 deletions
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 7eebfdf7204f..2777cea05cc0 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4851,18 +4851,20 @@ 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;
}