[PATCH v7 0/3] arm64/sve: Improve performance when handling SVE access traps

[Dave Martin]

On Wed, Jul 21, 2021 at 05:34:29PM +0100, Mark Brown wrote:
> On Wed, Jul 21, 2021 at 03:33:54PM +0100, Dave Martin wrote:
> 
> > While I think this was a worthwhile experiment, my concern here is that
> > while the approach taken in this series is reasonable, it doesn't seem
> > to reduce the amount of code or result in a net simplification.  From my
> > side I think it's probably best to stick with what we have, until
> > someone comes up with something that's clearly easier to understand.
> 
> I did find it was making it easier to understand some of what was going
> on TBH - I forget which specific bits but I found the whole model of
> specifying the goal state at a higher level clarified things for me.
> It's definitely not saving much in the way of code though and the code
> that was already merged to do the zeroing in place gives us most of the
> win with dramatically less code, it just doesn't help if we do context
> switch.
> 
> > So, I'd still favour the version based on Julien's code, which is more
> > of an incremental change to what we already had (and I think was most of
> > the way there in your post recent version of it).
> 
> I prefer Julien's approach too, the requirement to trigger the slow path
> on return to userspace doesn't really work with the newer approach
> AFAICT.  If this gets resurrected I'll go back to the last _NO_FLUSH
> version.

OK, sounds fair -- thanks for the patience.

Cheers
---Dave