KVM: x86: #undef SPEC_CTRL_SSBD in cpuid.c to avoid macro collisions

Undefine SPEC_CTRL_SSBD, which is #defined by msr-index.h to represent the
enable flag in MSR_IA32_SPEC_CTRL, to avoid issues with the macro being
unpacked into its raw value when passed to KVM's F() macro.  This will
allow using multiple layers of macros in F() and friends, e.g. to harden
against incorrect usage of F().

No functional change intended (cpuid.c doesn't consume SPEC_CTRL_SSBD).

Link: https://lore.kernel.org/r/20241128013424.4096668-28-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 2cd06155684ef10016ca57936f0340537263f7a5..cebb7314b9be55227a0010b52b1f433cf5031349 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -665,6 +665,12 @@ static __always_inline void kvm_cpu_cap_init(u32 leaf, u32 mask)
        feature_bit(name);                                                      \
 })
 
+/*
+ * Undefine the MSR bit macro to avoid token concatenation issues when
+ * processing X86_FEATURE_SPEC_CTRL_SSBD.
+ */
+#undef SPEC_CTRL_SSBD
+
 void kvm_set_cpu_caps(void)
 {
        memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps));