KVM: x86: Limit use of F() and SF() to kvm_cpu_cap_{mask,init_kvm_defined}()

Define and undefine the F() and SF() macros precisely around
kvm_set_cpu_caps() to make it all but impossible to use the macros outside
of kvm_cpu_cap_{mask,init_kvm_defined}().  Currently, F() is a simple
passthrough, but SF() is actively dangerous as it checks that the scattered
feature is supported by the host kernel.

And usage outside of the aforementioned helpers will run afoul of future
changes to harden KVM's CPUID management.

Opportunistically switch to feature_bit() when stuffing LA57 based on raw
hardware support.

No functional change intended.

Link: https://lore.kernel.org/r/20241128013424.4096668-3-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 701bbbf58124348ec5265bd6b84f52e93cd8bf67..3f52e6bdbe8e53c7cfc0f738b07ce7fc2ebd617f 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -82,15 +82,6 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
        return ret;
 }
 
-#define F feature_bit
-
-/* Scattered Flag - For features that are scattered by cpufeatures.h. */
-#define SF(name)                                               \
-({                                                             \
-       BUILD_BUG_ON(X86_FEATURE_##name >= MAX_CPU_FEATURES);   \
-       (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0);       \
-})
-
 /*
  * Magic value used by KVM when querying userspace-provided CPUID entries and
  * doesn't care about the CPIUD index because the index of the function in
@@ -625,6 +616,15 @@ static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
        __kvm_cpu_cap_mask(leaf);
 }
 
+#define F feature_bit
+
+/* Scattered Flag - For features that are scattered by cpufeatures.h. */
+#define SF(name)                                               \
+({                                                             \
+       BUILD_BUG_ON(X86_FEATURE_##name >= MAX_CPU_FEATURES);   \
+       (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0);       \
+})
+
 void kvm_set_cpu_caps(void)
 {
 #ifdef CONFIG_X86_64
@@ -689,7 +689,7 @@ void kvm_set_cpu_caps(void)
                F(SGX_LC) | F(BUS_LOCK_DETECT)
        );
        /* Set LA57 based on hardware capability. */
-       if (cpuid_ecx(7) & F(LA57))
+       if (cpuid_ecx(7) & feature_bit(LA57))
                kvm_cpu_cap_set(X86_FEATURE_LA57);
 
        /*
@@ -871,6 +871,9 @@ void kvm_set_cpu_caps(void)
 }
 EXPORT_SYMBOL_GPL(kvm_set_cpu_caps);
 
+#undef F
+#undef SF
+
 struct kvm_cpuid_array {
        struct kvm_cpuid_entry2 *entries;
        int maxnent;
@@ -946,14 +949,14 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func)
                ++array->nent;
                break;
        case 1:
-               entry->ecx = F(MOVBE);
+               entry->ecx = feature_bit(MOVBE);
                ++array->nent;
                break;
        case 7:
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                entry->eax = 0;
                if (kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
-                       entry->ecx = F(RDPID);
+                       entry->ecx = feature_bit(RDPID);
                ++array->nent;
                break;
        default:
@@ -1103,7 +1106,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                        goto out;
 
                cpuid_entry_override(entry, CPUID_D_1_EAX);
-               if (entry->eax & (F(XSAVES)|F(XSAVEC)))
+               if (entry->eax & (feature_bit(XSAVES) | feature_bit(XSAVEC)))
                        entry->ebx = xstate_required_size(permitted_xcr0 | permitted_xss,
                                                          true);
                else {
@@ -1648,7 +1651,7 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
                        u64 data;
                        if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&
                            (data & TSX_CTRL_CPUID_CLEAR))
-                               *ebx &= ~(F(RTM) | F(HLE));
+                               *ebx &= ~(feature_bit(RTM) | feature_bit(HLE));
                } else if (function == 0x80000007) {
                        if (kvm_hv_invtsc_suppressed(vcpu))
                                *edx &= ~feature_bit(CONSTANT_TSC);