Re: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync_core() when available

[hpa]

On July 27, 2020 1:36:19 AM PDT, peterz@xxxxxxxxxxxxx wrote:
>On Sun, Jul 26, 2020 at 10:55:15PM -0700, hpa@xxxxxxxxx wrote:
>> For a really overenginered solution, but which might perform
>> unnecessary poorly on existing hardware:
>> 
>> asm volatile("1: .byte 0xf, 0x1, 0xe8; 2:"
>>                         _ASM_EXTABLE(1b,2b));
>
>Ha! cute, you take an #UD ?
>
>We could optimize the #UD exception handler for this I suppose, but
>that
>makes it an even worse hack. The simple alternative() seems like a much
>simpler approach.

If this is in any way performance critical, then no :) Taking the #UD has the cute property that we end up IRET on the way back, so we don't even need a fix-up path.


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