linux-kernel - Re: [PATCH] selftests: x86: skip the tests if prerequisites aren't fulfilled

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Date: Tue, 12 Mar 2024 14:26:28 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: "Chang S. Bae" <chang.seok.bae@...el.com>, Shuah Khan <shuah@...nel.org>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Weihong Zhang <weihong.zhang@...el.com>,
 Binbin Wu <binbin.wu@...ux.intel.com>, angquan yu <angquan21@...il.com>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>, kernel@...labora.com,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: x86: skip the tests if prerequisites aren't
 fulfilled

On 3/11/24 10:39 PM, Chang S. Bae wrote:
> On 3/11/2024 10:02 AM, Muhammad Usama Anjum wrote:
>> On 3/9/24 6:06 AM, Chang S. Bae wrote:
>>> On 3/7/2024 10:37 AM, Muhammad Usama Anjum wrote:
>>>
>>>> -static void check_cpuid_xtiledata(void)
>>>> +static int check_cpuid_xtiledata(void)
>>>>    {
>>>>        uint32_t eax, ebx, ecx, edx;
>>>>    @@ -153,12 +160,16 @@ static void check_cpuid_xtiledata(void)
>>>>         * eax: XTILEDATA state component size
>>>>         * ebx: XTILEDATA state component offset in user buffer
>>>>         */
>>>> -    if (!eax || !ebx)
>>>> -        fatal_error("xstate cpuid: invalid tile data size/offset: %d/%d",
>>>> -                eax, ebx);
>>>> +    if (!eax || !ebx) {
>>>> +        ksft_print_msg("xstate cpuid: invalid tile data size/offset:
>>>> %d/%d\n",
>>>> +                   eax, ebx);
>>>> +        return -1;
>>>> +    }
>>>>          xtiledata.size          = eax;
>>>>        xtiledata.xbuf_offset = ebx;
>>>> +
>>>> +    return 0;
>>>>    }
>>>
>>> I don't think it is okay to silently skip the test here. If the feature is
>>> available, the tile data size and offset should not be zero.
>> We are logging that data size/offset are invalid if either eax or ebx are
>> invalid and then we are skipping. Not sure what you are asking me to change.
> 
> You intention seems to skip the test when AMX is not available. 
Yes,

> But this
> function should only be invoked when AMX is actually available, not as part
> of the feature availability check. 
How can we check if AMX is available or not?

> Therefore, I think this change is not
> relevant. Also, if we encounter invalid TILEDATA CPUID, it should be a
> reason to *fail* the test, rather than calling out a skip, right?
I see. But once we check if AMX is available.

> 
> Thanks,
> Chang
> 

-- 
BR,
Muhammad Usama Anjum