x86/virt: KVM: Open code cpu_has_vmx() in KVM VMX

Fold the raw CPUID check for VMX into kvm_is_vmx_supported(), its sole
user.  Keep the check even though KVM also checks X86_FEATURE_VMX, as the
intent is to provide a unique error message if VMX is unsupported by
hardware, whereas X86_FEATURE_VMX may be clear due to firmware and/or
kernel actions.

No functional change intended.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/include/asm/virtext.h

@@ -22,14 +22,6 @@
 /*
  * VMX functions:
  */
-
-static inline int cpu_has_vmx(void)
-{
-	unsigned long ecx = cpuid_ecx(1);
-	return test_bit(5, &ecx); /* CPUID.1:ECX.VMX[bit 5] -> VT */
-}
-
-
 /**
  * cpu_vmxoff() - Disable VMX on the current CPU
  *
@@ -61,8 +53,6 @@ static inline int cpu_vmx_enabled(void)
 }
 
 /** Disable VMX if it is enabled on the current CPU
- *
- * You shouldn't call this if cpu_has_vmx() returns 0.
  */
 static inline void __cpu_emergency_vmxoff(void)
 {

arch/x86/kvm/vmx/vmx.c

@@ -2699,7 +2699,7 @@ static bool kvm_is_vmx_supported(void)
 {
 	int cpu = raw_smp_processor_id();
 
-	if (!cpu_has_vmx()) {
+	if (!(cpuid_ecx(1) & feature_bit(VMX))) {
 		pr_err("VMX not supported by CPU %d\n", cpu);
 		return false;
 	}