KVM: x86: Introduce kvm_cpu_caps to replace runtime CPUID masking

Calculate the CPUID masks for KVM_GET_SUPPORTED_CPUID at load time using
what is effectively a KVM-adjusted copy of boot_cpu_data, or more
precisely, the x86_capability array in boot_cpu_data.

In terms of KVM support, the vast majority of CPUID feature bits are
constant, and *all* feature support is known at KVM load time.  Rather
than apply boot_cpu_data, which is effectively read-only after init,
at runtime, copy it into a KVM-specific array and use *that* to mask
CPUID registers.

In additional to consolidating the masking, kvm_cpu_caps can be adjusted
by SVM/VMX at load time and thus eliminate all feature bit manipulation
in ->set_supported_cpuid().

Opportunistically clean up a few warts:

  - Replace bare "unsigned" with "unsigned int" when a feature flag is
    captured in a local variable, e.g. f_nx.

  - Sort the CPUID masks by function, index and register (alphabetically
    for registers, i.e. EBX comes before ECX/EDX).

  - Remove the superfluous /* cpuid 7.0.ecx */ comments.

No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
[Call kvm_set_cpu_caps from kvm_x86_ops->hardware_setup due to fixed
 GBPAGES patch. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.h

@@ -6,6 +6,9 @@
 #include <asm/cpu.h>
 #include <asm/processor.h>
 
+extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
+void kvm_set_cpu_caps(void);
+
 int kvm_update_cpuid(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
 					      u32 function, u32 index);
@@ -172,7 +175,8 @@ static __always_inline void cpuid_entry_mask(struct kvm_cpuid_entry2 *entry,
 {
 	u32 *reg = cpuid_entry_get_reg(entry, leaf * 32);
 
-	*reg &= boot_cpu_data.x86_capability[leaf];
+	BUILD_BUG_ON(leaf >= ARRAY_SIZE(kvm_cpu_caps));
+	*reg &= kvm_cpu_caps[leaf];
 }
 
 static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu,
@@ -262,4 +266,20 @@ static inline bool cpuid_fault_enabled(struct kvm_vcpu *vcpu)
 		  MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
 }
 
+static __always_inline void kvm_cpu_cap_clear(unsigned int x86_feature)
+{
+	unsigned int x86_leaf = x86_feature / 32;
+
+	reverse_cpuid_check(x86_leaf);
+	kvm_cpu_caps[x86_leaf] &= ~__feature_bit(x86_feature);
+}
+
+static __always_inline void kvm_cpu_cap_set(unsigned int x86_feature)
+{
+	unsigned int x86_leaf = x86_feature / 32;
+
+	reverse_cpuid_check(x86_leaf);
+	kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
+}
+
 #endif

arch/x86/kvm/svm.c

@@ -1479,6 +1479,8 @@ static __init int svm_hardware_setup(void)
 			pr_info("Virtual GIF supported\n");
 	}
 
+	kvm_set_cpu_caps();
+
 	return 0;
 
 err:

arch/x86/kvm/vmx/vmx.c

@@ -7818,6 +7818,8 @@ static __init int hardware_setup(void)
 			return r;
 	}
 
+	kvm_set_cpu_caps();
+
 	r = alloc_kvm_area();
 	if (r)
 		nested_vmx_hardware_unsetup();