[PATCH v3 05/11] KVM: arm64: Eagerly restore host fpsimd/sve state in pKVM

[Marc Zyngier]

On Mon, 03 Jun 2024 15:15:37 +0100,
Mark Brown <broonie at kernel.org> wrote:
> 
> On Mon, Jun 03, 2024 at 02:48:39PM +0100, Marc Zyngier wrote:
> > Mark Brown <broonie at kernel.org> wrote:
> > > On Mon, Jun 03, 2024 at 09:37:16AM +0100, Fuad Tabba wrote:
> 
> > > > Also, one of the concerns in terms of performance is now with
> > > > nested-virt support being added, and the overhead of doing the
> > > > conditional update when we know that it's unlikely that anyone is
> > > > implementing vectors as big as the max.
> 
> > > I guess there's the option of doing a restore of a value fixed during
> > > initialisation instead?
> 
> > And what do we gain from that?
> 
> Reducing the number of places that need updating.

That'd be assuming that the host side value never requires any change
and will be OK with a fixed value. Given that this highly hypothetical
change would be likely to be a hierarchical control much like ZCR_ELx
is today, the fixed value is likely to change on a regular basis.

In any case, this is something we can (re)evaluate when we get to it.
If ever.

	M.

-- 
Without deviation from the norm, progress is not possible.