KVM: SVM: Disallow EFER.LMSLE when not supported by hardware

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Modern AMD CPUs do not support segment limit checks in 64-bit mode
(i.e. EFER.LMSLE must be zero). Do not allow a guest to set EFER.LMSLE
on a CPU that requires the bit to be zero.

For backwards compatibility, allow EFER.LMSLE to be set on CPUs that
support segment limit checks in 64-bit mode, even though KVM's
implementation of the feature is incomplete (e.g. KVM's emulator does
not enforce segment limits in 64-bit mode).

Fixes: eec4b140c9 ("KVM: SVM: Allow EFER.LMSLE to be set with nested svm")

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://lore.kernel.org/r/20251001001529.1119031-3-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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Jim Mattson 2025-09-30 17:14:08 -07:00 • committed by Sean Christopherson

parent 4793f990ea

commit c53c632592

1 changed files with 3 additions and 1 deletions

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arch/x86/kvm/svm/svm.c

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