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SubjectRe: [PATCH v1 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD
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On 3/27/2021 8:18 AM, Kuppuswamy Sathyanarayanan wrote:
> In non-root TDX guest mode, MWAIT, MONITOR and WBINVD instructions
> are not supported. So handle #VE due to these instructions as no ops.
>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Reviewed-by: Andi Kleen <ak@linux.intel.com>
> ---
>
> Changes since previous series:
> * Suppressed MWAIT feature as per Andi's comment.
> * Added warning debug log for MWAIT #VE exception.
>
> arch/x86/kernel/tdx.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
> index e936b2f88bf6..fb7d22b846fc 100644
> --- a/arch/x86/kernel/tdx.c
> +++ b/arch/x86/kernel/tdx.c
> @@ -308,6 +308,9 @@ void __init tdx_early_init(void)
>
> setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
>
> + /* MWAIT is not supported in TDX platform, so suppress it */
> + setup_clear_cpu_cap(X86_FEATURE_MWAIT);

In fact, MWAIT bit returned by CPUID instruction is zero for TD guest.
This is enforced by SEAM module.

Do we still need to safeguard it by setup_clear_cpu_cap() here?

> +
> tdg_get_info();
>
> pv_ops.irq.safe_halt = tdg_safe_halt;


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