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From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <sean.j.christopherson@intel.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, Dan Cross <dcross@google.com>,
        Peter Shier <pshier@google.com>
Subject: [PATCH 7/7] KVM: nVMX: WARN on attempt to switch the currently loaded VMCS
Date:   Tue, 14 Jul 2020 21:05:57 -0700
Message-Id: <20200715040557.5889-8-sean.j.christopherson@intel.com>
In-Reply-To: <20200715040557.5889-1-sean.j.christopherson@intel.com>
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WARN if KVM attempts to switch to the currently loaded VMCS.  Now that
nested_vmx_free_vcpu() doesn't blindly call vmx_switch_vmcs(), all paths
that lead to vmx_switch_vmcs() are implicitly guarded by guest vs. host
mode, e.g. KVM should never emulate VMX instructions when guest mode is
active, and nested_vmx_vmexit() should never be called when host mode is
active.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/vmx/nested.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 66ed449f0d59f..023055e636d61 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -258,7 +258,7 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
 	struct loaded_vmcs *prev;
 	int cpu;
 
-	if (vmx->loaded_vmcs == vmcs)
+	if (WARN_ON_ONCE(vmx->loaded_vmcs == vmcs))
 		return;
 
 	cpu = get_cpu();
-- 
2.26.0