linux-kernel - [PATCH v3 24/57] KVM: x86: Add a macro to init CPUID features that are 64-bit only

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Message-ID: <20241128013424.4096668-25-seanjc@google.com>
Date: Wed, 27 Nov 2024 17:33:51 -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 24/57] 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@...hat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/cpuid.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 9bd8bac3cd52..9219e164c810 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -642,17 +642,14 @@ 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)) >
@@ -859,7 +856,7 @@ 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,
@@ -920,10 +917,10 @@ 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)
 	);
@@ -1057,6 +1054,7 @@ EXPORT_SYMBOL_GPL(kvm_set_cpu_caps);
 
 #undef F
 #undef SF
+#undef X86_64_F
 
 struct kvm_cpuid_array {
 	struct kvm_cpuid_entry2 *entries;
-- 
2.47.0.338.g60cca15819-goog