Re: [PATCH v4 6/7] KVM: selftests: Add coverage for LASS CPUID and CR4 handling

[Binbin Wu]

On 8/6/2026 9:15 AM, Sohil Mehta wrote:
> Add a LASS selftest for KVM's handling of CPUID advertisement and
> CR4.LASS. Verify that a guest write to CR4.LASS generates #GP, and
> leaves CR4 unchanged, when LASS isn't enumerated in the guest's CPUID.
> 
> Extend set_sregs_test to cover CR4.LASS and verify that KVM_SET_SREGS
> accepts CR4.LASS when LASS is supported, and rejects it, without
> modifying sregs, when it isn't.
> 
> Don't try running with CR4.LASS enabled in the guest or attempt to
> trigger LASS violations. Selftests run guest code in the lower half of
> the address space at CPL0, so enabling CR4.LASS would make the next
> instruction fetch a violation and triple-fault the guest.
> 
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>

Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>