diff mbox series

[02/15] x86/cpufeatures: Add CPUID_LNX_5 to track recently added Linux-defined word

Message ID 20240517075728.9722-3-yuxuan.luo@canonical.com
State New
Headers show
Series CVE-2024-2201 | expand

Commit Message

Yuxuan Luo May 17, 2024, 7:57 a.m. UTC 
From: Sean Christopherson <seanjc@google.com>

Add CPUID_LNX_5 to track cpufeatures' word 21, and add the appropriate
compile-time assert in KVM to prevent direct lookups on the features in
CPUID_LNX_5.  KVM uses X86_FEATURE_* flags to manage guest CPUID, and so
must translate features that are scattered by Linux from the Linux-defined
bit to the hardware-defined bit, i.e. should never try to directly access
scattered features in guest CPUID.

Opportunistically add NR_CPUID_WORDS to enum cpuid_leafs, along with a
compile-time assert in KVM's CPUID infrastructure to ensure that future
additions update cpuid_leafs along with NCAPINTS.

No functional change intended.

Fixes: 7f274e609f3d ("x86/cpufeatures: Add new word for scattered features")
Cc: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(backported from commit 8cb4a9a82b21623dbb4b3051dd30d98356cf95bc)
[yuxuan.luo: crops the build checks from reverse_cpuid.h to cpuid.h
 since reverse_cpuid is yet to be introduced.
]
CVE-2024-2201
Signed-off-by: Yuxuan Luo <yuxuan.luo@canonical.com>
---
 arch/x86/include/asm/cpufeature.h | 2 ++
 arch/x86/kvm/cpuid.h              | 2 ++
 2 files changed, 4 insertions(+)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 41cb0cbbfdebf..6611478530810 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -32,6 +32,8 @@  enum cpuid_leafs
 	CPUID_7_EDX,
 	CPUID_8000_001F_EAX,
 	CPUID_8000_0021_EAX,
+	CPUID_LNX_5,
+	NR_CPUID_WORDS,
 };
 
 #ifdef CONFIG_X86_FEATURE_NAMES
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index defae8082789f..50d426d3af08f 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -60,6 +60,8 @@  static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned x86_feature)
 {
 	unsigned x86_leaf = x86_feature / 32;
 
+	BUILD_BUG_ON(NR_CPUID_WORDS != NCAPINTS);
+	BUILD_BUG_ON(x86_leaf == CPUID_LNX_5);
 	BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
 	BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);