linux-kernel - Re: [PATCH v4 2/2] selftests/x86/amx: Update the ARCH_REQ_XCOMP

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Date:   Wed, 23 Mar 2022 17:44:59 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, mingo@...hat.com
Cc:     yang.zhong@...el.com, ravi.v.shankar@...el.com,
        chang.seok.bae@...el.com, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 2/2] selftests/x86/amx: Update the
 ARCH_REQ_XCOMP_PERM test

On Sat, Jan 29 2022 at 09:36, Chang S. Bae wrote:
> Update the arch_prctl test to check the permission bitmap whether the
> requested feature is added as expected or not.
>
> Every non-dynamic feature that is enabled is permitted already for use.
> TILECFG is not dynamic feature. Ensure the bit is always on from
> ARCH_GET_XCOMP_PERM.

Running it on a machine which does not have AMX results in:

 amx_64: [FAIL]	xstate cpuid: invalid tile data size/offset: 0/0: Success

It's not a failure, really. Selftests are supposed to run on all
machines and the proper thing to do if a hardware feature is not
available is to SKIP the test and return 0.

Thanks,

        tglx