[PATCH 5.10 500/545] KVM: VMX: Drop explicit nested check from vmx_set_cr4()

Greg Kroah-Hartman
2022-08-19T16:47:43Z

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