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[v3,3/8] KVM: x86: Clear all supported AVX-512 xfeatures if they are not all set

Message ID 20230224223607.1580880-4-aaronlewis@google.com (mailing list archive)
State New, archived
Headers show
Series Clean up the supported xfeatures | expand

Commit Message

Aaron Lewis Feb. 24, 2023, 10:36 p.m. UTC 
Be a good citizen and don't allow any of the supported AVX-512
xfeatures[1] to be set if they can't all be set.  That way userspace or
a guest doesn't fail if it attempts to set them in XCR0.

[1] CPUID.(EAX=0DH,ECX=0):EAX.OPMASK[bit-5]
    CPUID.(EAX=0DH,ECX=0):EAX.ZMM_Hi256[bit-6]
    CPUID.(EAX=0DH,ECX=0):EAX.ZMM_Hi16_ZMM[bit-7]

Suggested-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
 arch/x86/kvm/cpuid.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b2e7407cd114..76379a51a16d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -68,6 +68,10 @@  static u64 sanitize_xcr0(u64 xcr0)
 	if ((xcr0 & mask) != mask)
 		xcr0 &= ~mask;
 
+	mask = XFEATURE_MASK_AVX512;
+	if ((xcr0 & mask) != mask)
+		xcr0 &= ~XFEATURE_MASK_AVX512;
+
 	return xcr0;
 }