On 12.05.21 15:24, Andi Kleen wrote:
> 
> On 5/12/2021 6:18 AM, Peter Zijlstra wrote:
>> On Mon, May 10, 2021 at 05:56:05PM +0200, Juergen Gross wrote:
>>
>>> No. We have PARAVIRT_XXL for Xen PV guests, and we have PARAVIRT for
>>> other hypervisor's guests, supporting basically the TLB flush operations
>>> and time related operations only. Adding the halt related operations to
>>> PARAVIRT wouldn't break anything.
>> Also, I don't think anything modern should actually ever hit any of the
>> HLT instructions, most everything should end up at an MWAIT.
>>
>> Still, do we wants to give arch_safe_halt() and halt() the
>> PVOP_ALT_VCALL0() treatment?
> 
>  From performance reasons it's pointless to patch. HLT (and MWAIT) are 
> so slow anyways that using patching or an indirect pointer is completely 
> in the noise. So I would use whatever is cleanest in the code.

This would probably be x86_platform_ops.hyper hooks.


Juergen