KVM: x86: Bury guest_cpuid_is_amd_or_hygon() in cpuid.c

Move guest_cpuid_is_amd_or_hygon() into cpuid.c now that, except for one
Intel quirk in the emulator, KVM checks for AMD vs. Intel *compatible*
vCPUs, not exact vendors, i.e. now that there should not be any reason for
KVM at-large to care about the exact vendor.

Opportunistically refactor the guts of the helper to use "entry" instead
of "best", and short circuit the !entry path to make the common case more
readable.

Link: https://lore.kernel.org/r/20240405235603.1173076-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/cpuid.c

@@ -335,6 +335,18 @@ static bool kvm_cpuid_has_hyperv(struct kvm_cpuid_entry2 *entries, int nent)
 #endif
 }
 
+static bool guest_cpuid_is_amd_or_hygon(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *entry;
+
+	entry = kvm_find_cpuid_entry(vcpu, 0);
+	if (!entry)
+		return false;
+
+	return is_guest_vendor_amd(entry->ebx, entry->ecx, entry->edx) ||
+	       is_guest_vendor_hygon(entry->ebx, entry->ecx, entry->edx);
+}
+
 static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct kvm_lapic *apic = vcpu->arch.apic;

arch/x86/kvm/cpuid.h

@@ -102,16 +102,6 @@ static __always_inline void guest_cpuid_clear(struct kvm_vcpu *vcpu,
 		*reg &= ~__feature_bit(x86_feature);
 }
 
-static inline bool guest_cpuid_is_amd_or_hygon(struct kvm_vcpu *vcpu)
-{
-	struct kvm_cpuid_entry2 *best;
-
-	best = kvm_find_cpuid_entry(vcpu, 0);
-	return best &&
-	       (is_guest_vendor_amd(best->ebx, best->ecx, best->edx) ||
-		is_guest_vendor_hygon(best->ebx, best->ecx, best->edx));
-}
-
 static inline bool guest_cpuid_is_amd_compatible(struct kvm_vcpu *vcpu)
 {
 	return vcpu->arch.is_amd_compatible;