linux-kernel - [PATCH v3 25/57] KVM: x86: Add a macro to precisely handle aliased 0x1.EDX CPUID features

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Message-ID: <20241128013424.4096668-26-seanjc@google.com>
Date: Wed, 27 Nov 2024 17:33:52 -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 25/57] KVM: x86: Add a macro to precisely handle aliased
 0x1.EDX CPUID features

Add a macro to precisely handle CPUID features that AMD duplicated from
CPUID.0x1.EDX into CPUID.0x8000_0001.EDX.  This will allow adding an
assert that all features passed to kvm_cpu_cap_init() match the word being
processed, e.g. to prevent passing a feature from CPUID 0x7 to CPUID 0x1.

Because the kernel simply reuses the X86_FEATURE_* definitions from
CPUID.0x1.EDX, KVM's use of the aliased features would result in false
positives from such an assert.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/cpuid.c | 47 +++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 9219e164c810..ddff0c7c78b9 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -648,6 +648,16 @@ static __always_inline void kvm_cpu_cap_init(enum cpuid_leafs leaf, u32 mask)
 	(IS_ENABLED(CONFIG_X86_64) ? F(name) : 0);		\
 })
 
+/*
+ * Aliased Features - For features in 0x8000_0001.EDX that are duplicates of
+ * identical 0x1.EDX features, and thus are aliased from 0x1 to 0x8000_0001.
+ */
+#define ALIASED_1_EDX_F(name)							\
+({										\
+	BUILD_BUG_ON(__feature_leaf(X86_FEATURE_##name) != CPUID_1_EDX);	\
+	feature_bit(name);							\
+})
+
 void kvm_set_cpu_caps(void)
 {
 	memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps));
@@ -892,30 +902,30 @@ void kvm_set_cpu_caps(void)
 	);
 
 	kvm_cpu_cap_init(CPUID_8000_0001_EDX,
-		F(FPU) |
-		F(VME) |
-		F(DE) |
-		F(PSE) |
-		F(TSC) |
-		F(MSR) |
-		F(PAE) |
-		F(MCE) |
-		F(CX8) |
-		F(APIC) |
+		ALIASED_1_EDX_F(FPU) |
+		ALIASED_1_EDX_F(VME) |
+		ALIASED_1_EDX_F(DE) |
+		ALIASED_1_EDX_F(PSE) |
+		ALIASED_1_EDX_F(TSC) |
+		ALIASED_1_EDX_F(MSR) |
+		ALIASED_1_EDX_F(PAE) |
+		ALIASED_1_EDX_F(MCE) |
+		ALIASED_1_EDX_F(CX8) |
+		ALIASED_1_EDX_F(APIC) |
 		0 /* Reserved */ |
 		F(SYSCALL) |
-		F(MTRR) |
-		F(PGE) |
-		F(MCA) |
-		F(CMOV) |
-		F(PAT) |
-		F(PSE36) |
+		ALIASED_1_EDX_F(MTRR) |
+		ALIASED_1_EDX_F(PGE) |
+		ALIASED_1_EDX_F(MCA) |
+		ALIASED_1_EDX_F(CMOV) |
+		ALIASED_1_EDX_F(PAT) |
+		ALIASED_1_EDX_F(PSE36) |
 		0 /* Reserved */ |
 		F(NX) |
 		0 /* Reserved */ |
 		F(MMXEXT) |
-		F(MMX) |
-		F(FXSR) |
+		ALIASED_1_EDX_F(MMX) |
+		ALIASED_1_EDX_F(FXSR) |
 		F(FXSR_OPT) |
 		X86_64_F(GBPAGES) |
 		F(RDTSCP) |
@@ -1055,6 +1065,7 @@ EXPORT_SYMBOL_GPL(kvm_set_cpu_caps);
 #undef F
 #undef SF
 #undef X86_64_F
+#undef ALIASED_1_EDX_F
 
 struct kvm_cpuid_array {
 	struct kvm_cpuid_entry2 *entries;
-- 
2.47.0.338.g60cca15819-goog