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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 500/545] KVM: VMX: Drop explicit nested check from vmx_set_cr4()
Date:   Fri, 19 Aug 2022 17:44:30 +0200
Message-Id: <20220819153851.866986742@linuxfoundation.org>
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From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit a447e38a7fadb2e554c3942dda183e55cccd5df0 ]

Drop vmx_set_cr4()'s explicit check on the 'nested' module param now
that common x86 handles the check by incorporating VMXE into the CR4
reserved bits, via kvm_cpu_caps.  X86_FEATURE_VMX is set in kvm_cpu_caps
(by vmx_set_cpu_caps()), if and only if 'nested' is true.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201007014417.29276-3-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/vmx/vmx.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1b75847d8a49..154ec5d8cdf5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3211,18 +3211,13 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 		}
 	}
 
-	if (cr4 & X86_CR4_VMXE) {
-		/*
-		 * To use VMXON (and later other VMX instructions), a guest
-		 * must first be able to turn on cr4.VMXE (see handle_vmon()).
-		 * So basically the check on whether to allow nested VMX
-		 * is here.  We operate under the default treatment of SMM,
-		 * so VMX cannot be enabled under SMM.  Note, guest CPUID is
-		 * intentionally ignored, it's handled by cr4_guest_rsvd_bits.
-		 */
-		if (!nested || is_smm(vcpu))
-			return 1;
-	}
+	/*
+	 * We operate under the default treatment of SMM, so VMX cannot be
+	 * enabled under SMM.  Note, whether or not VMXE is allowed at all is
+	 * handled by kvm_valid_cr4().
+	 */
+	if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu))
+		return 1;
 
 	if (vmx->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
 		return 1;
-- 
2.35.1