linux-kernel - [PATCH v3 27/57] KVM: x86: #undef SPEC_CTRL_SSBD in cpuid.c to avoid macro collisions

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Message-ID: <20241128013424.4096668-28-seanjc@google.com>
Date: Wed, 27 Nov 2024 17:33:54 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, Jarkko Sakkinen <jarkko@...nel.org>
Cc: kvm@...r.kernel.org, linux-sgx@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>, 
	Hou Wenlong <houwenlong.hwl@...group.com>, Xiaoyao Li <xiaoyao.li@...el.com>, 
	Kechen Lu <kechenl@...dia.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Yang Weijiang <weijiang.yang@...el.com>, 
	Robert Hoo <robert.hoo.linux@...il.com>
Subject: [PATCH v3 27/57] 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).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/cpuid.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 73e756d097e4..efff83da3df3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -644,6 +644,12 @@ 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));
-- 
2.47.0.338.g60cca15819-goog