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SubjectRE: [PATCH v7 03/10] x86, mpx: add macro cpu_has_mpx
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On 2014-07-24, Hansen, Dave wrote:
> On 07/23/2014 05:56 PM, Ren, Qiaowei wrote:
>> On 2014-07-24, Hansen, Dave wrote:
>>> On 07/22/2014 07:35 PM, Ren, Qiaowei wrote:
>>>> The checking about MPX feature should be as follow:
>>>>
>>>> if (pcntxt_mask & XSTATE_EAGER) {
>>>> if (eagerfpu == DISABLE) {
>>>> pr_err("eagerfpu not present, disabling
> some
>>> xstate features: 0x%llx\n",
>>>> pcntxt_mask &
>>> XSTATE_EAGER);
>>>> pcntxt_mask &= ~XSTATE_EAGER; } else {
>>>> eagerfpu = ENABLE;
>>>> }
>>>> }
>>>> This patch was merged into kernel the ending of last year
>>>> (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/c
>>>> om
>>>> mi
>>>> t/?id=e7d820a5e549b3eb6c3f9467507566565646a669 )
>>>
>>> Should we be doing a clear_cpu_cap(X86_FEATURE_MPX) in here?
>>>
>>> This isn't major, but I can't _ever_ imagine a user being able to
>>> track down why MPX is not working from this message. Should we
>>> spruce it up somehow?
>>
>> Maybe. If the error log "disabling some xstate features:" is changed
>> to "disabling MPX xstate features:", do you think it is OK?
>
> That's better. Is it really disabling MPX, though?
>
> And shouldn't we clear the cpu feature bit too?

I am not sure. I am suspecting whether this checking should be moved before xstate_enable().

Peter, what do you think of it?

Thanks,
Qiaowei



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