Re: [PATCH v4 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support

[Marc Zyngier]

On 2020-11-27 17:24, Quentin Perret wrote:
> On Friday 27 Nov 2020 at 17:14:11 (+0000), Marc Zyngier wrote:

[...]

> > Yeah, the sanitized read feels better, if only because that is
> > what we are going to read in all the valid cases, unfortunately.
> > read_sanitised_ftr_reg() is sadly not designed to be called on
> > a fast path, meaning that 32bit guests will do a bsearch() on
> > the ID-regs every time they exit...
> >
> > I guess we will have to evaluate how much we loose with this.
>
> Could we use the trick we have for arm64_ftr_reg_ctrel0 to speed this
> up?

Maybe. I want to first verify whether this has any measurable impact.
Another possibility would be to cache the last read_sanitised_ftr_reg()
access, just to see if that helps. There shouldn't be that many code
paths hammering it.

Thanks,

        M.
--
Jazz is not dead. It just smells funny...