linux-kernel - [PATCH v2 22/49] KVM: x86: Add a macro to precisely handle aliased 0x1.EDX CPUID features

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Date: Fri, 17 May 2024 10:38:59 -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 22/49] 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 | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 5e3b97d06374..f2bd2f5c4ea3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -88,6 +88,16 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
 	F(name);						\
 })
 
+/*
+ * 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 AF(name)								\
+({										\
+	BUILD_BUG_ON(__feature_leaf(X86_FEATURE_##name) != CPUID_1_EDX);	\
+	feature_bit(name);							\
+})
+
 /*
  * Magic value used by KVM when querying userspace-provided CPUID entries and
  * doesn't care about the CPIUD index because the index of the function in
@@ -758,13 +768,13 @@ 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) | 0 /* Reserved */ | F(SYSCALL) |
-		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) | X86_64_F(GBPAGES) | F(RDTSCP) |
+		AF(FPU) | AF(VME) | AF(DE) | AF(PSE) |
+		AF(TSC) | AF(MSR) | AF(PAE) | AF(MCE) |
+		AF(CX8) | AF(APIC) | 0 /* Reserved */ | F(SYSCALL) |
+		AF(MTRR) | AF(PGE) | AF(MCA) | AF(CMOV) |
+		AF(PAT) | AF(PSE36) | 0 /* Reserved */ |
+		F(NX) | 0 /* Reserved */ | F(MMXEXT) | AF(MMX) |
+		AF(FXSR) | F(FXSR_OPT) | X86_64_F(GBPAGES) | F(RDTSCP) |
 		0 /* Reserved */ | X86_64_F(LM) | F(3DNOWEXT) | F(3DNOW)
 	);
 
-- 
2.45.0.215.g3402c0e53f-goog