linux-kernel - [PATCH v2 21/49] KVM: x86: Add a macro to init CPUID features that are 64-bit only

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Date: Fri, 17 May 2024 10:38:58 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Hou Wenlong <houwenlong.hwl@...group.com>, Kechen Lu <kechenl@...dia.com>, 
	Oliver Upton <oliver.upton@...ux.dev>, Maxim Levitsky <mlevitsk@...hat.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Yang Weijiang <weijiang.yang@...el.com>, 
	Robert Hoo <robert.hoo.linux@...il.com>
Subject: [PATCH v2 21/49] 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.

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 5a4d6138c4f1..5e3b97d06374 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -70,6 +70,12 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
 	(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);		\
+})
+
 /*
  * Raw Feature - For features that KVM supports based purely on raw host CPUID,
  * i.e. that KVM virtualizes even if the host kernel doesn't use the feature.
@@ -639,15 +645,6 @@ static __always_inline void kvm_cpu_cap_init(enum cpuid_leafs leaf, u32 mask)
 
 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)) >
@@ -744,7 +741,8 @@ void kvm_set_cpu_caps(void)
 	);
 
 	kvm_cpu_cap_init(CPUID_D_1_EAX,
-		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES) | f_xfd
+		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES) |
+		X86_64_F(XFD)
 	);
 
 	kvm_cpu_cap_init_kvm_defined(CPUID_12_EAX,
@@ -766,8 +764,8 @@ void kvm_set_cpu_caps(void)
 		F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
 		F(PAT) | F(PSE36) | 0 /* Reserved */ |
 		F(NX) | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
-		F(FXSR) | F(FXSR_OPT) | f_gbpages | F(RDTSCP) |
-		0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW)
+		F(FXSR) | F(FXSR_OPT) | X86_64_F(GBPAGES) | F(RDTSCP) |
+		0 /* Reserved */ | X86_64_F(LM) | F(3DNOWEXT) | F(3DNOW)
 	);
 
 	if (!tdp_enabled && IS_ENABLED(CONFIG_X86_64))
-- 
2.45.0.215.g3402c0e53f-goog