Re: [RFC v2 01/32] x86/paravirt: Introduce CONFIG_PARAVIRT_XL

[Juergen Gross]

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

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