KVM: x86: Add a macro to init CPUID features that are 64-bit only

Add a macro to mask-in feature flags that are supported only on 64-bit
kernels/KVM.  In addition to reducing overall #ifdeffery, using a macro
will allow hardening the kvm_cpu_cap initialization sequences to assert
that the features being advertised are indeed included in the word being
initialized.  And arguably using *F() macros through is more readable.

No functional change intended.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-25-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 5546ec57239215e3833abe6bc54a74d6c18ba9d2..bd1d54e25414e4ce9d0a6a609e50a590c6bd8f9c 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -663,17 +663,14 @@ static __always_inline void kvm_cpu_cap_init(enum cpuid_leafs leaf, u32 mask)
        (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0);       \
 })
 
+/* Features that KVM supports only on 64-bit kernels. */
+#define X86_64_F(name)                                         \
+({                                                             \
+       (IS_ENABLED(CONFIG_X86_64) ? F(name) : 0);              \
+})
+
 void kvm_set_cpu_caps(void)
 {
-#ifdef CONFIG_X86_64
-       unsigned int f_gbpages = F(GBPAGES);
-       unsigned int f_lm = F(LM);
-       unsigned int f_xfd = F(XFD);
-#else
-       unsigned int f_gbpages = 0;
-       unsigned int f_lm = 0;
-       unsigned int f_xfd = 0;
-#endif
        memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps));
 
        BUILD_BUG_ON(sizeof(kvm_cpu_caps) - (NKVMCAPINTS * sizeof(*kvm_cpu_caps)) >
@@ -880,7 +877,7 @@ void kvm_set_cpu_caps(void)
                F(XSAVEC) |
                F(XGETBV1) |
                F(XSAVES) |
-               f_xfd
+               X86_64_F(XFD)
        );
 
        kvm_cpu_cap_init_kvm_defined(CPUID_12_EAX,
@@ -941,10 +938,10 @@ void kvm_set_cpu_caps(void)
                F(MMX) |
                F(FXSR) |
                F(FXSR_OPT) |
-               f_gbpages |
+               X86_64_F(GBPAGES) |
                F(RDTSCP) |
                0 /* Reserved */ |
-               f_lm |
+               X86_64_F(LM) |
                F(3DNOWEXT) |
                F(3DNOW)
        );
@@ -1078,6 +1075,7 @@ EXPORT_SYMBOL_GPL(kvm_set_cpu_caps);
 
 #undef F
 #undef SF
+#undef X86_64_F
 
 struct kvm_cpuid_array {
        struct kvm_cpuid_entry2 *entries;