KVM: x86: Use KVM cpu caps to mark CR4.LA57 as not-reserved

Add accessor(s) for KVM cpu caps and use said accessor to detect
hardware support for LA57 instead of manually querying CPUID.

Note, the explicit conversion to bool via '!!' in kvm_cpu_cap_has() is
technically unnecessary, but it gives people a warm fuzzy feeling.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.h

@@ -282,6 +282,19 @@ static __always_inline void kvm_cpu_cap_set(unsigned int x86_feature)
 	kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
 }
 
+static __always_inline u32 kvm_cpu_cap_get(unsigned int x86_feature)
+{
+	unsigned int x86_leaf = x86_feature / 32;
+
+	reverse_cpuid_check(x86_leaf);
+	return kvm_cpu_caps[x86_leaf] & __feature_bit(x86_feature);
+}
+
+static __always_inline bool kvm_cpu_cap_has(unsigned int x86_feature)
+{
+	return !!kvm_cpu_cap_get(x86_feature);
+}
+
 static __always_inline void kvm_cpu_cap_check_and_set(unsigned int x86_feature)
 {
 	if (boot_cpu_has(x86_feature))

arch/x86/kvm/x86.c

@@ -925,7 +925,7 @@ static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
 {
 	u64 reserved_bits = __cr4_reserved_bits(cpu_has, c);
 
-	if (cpuid_ecx(0x7) & feature_bit(LA57))
+	if (kvm_cpu_cap_has(X86_FEATURE_LA57))
 		reserved_bits &= ~X86_CR4_LA57;
 
 	if (kvm_x86_ops->umip_emulated())