[PATCH v4 0/8] arm64/sve: First steps towards optimizing syscalls

Will Deacon will at kernel.org
Mon Sep 21 08:42:13 EDT 2020

On Fri, Aug 28, 2020 at 07:11:47PM +0100, Mark Brown wrote:
> This is a first attempt to optimize the syscall path when the user
> application uses SVE. The patch series was originally written by Julien
> Grall but has been left for a long time, I've updated it to current
> kernels and tried to address the pending review feedback that I found
> (which was mostly documentation issues). I may have missed some things
> there, apologies if I did, and one thing I've not yet done is produced a
> diagram of the states the relevant TIF_ flags can have - I need to work
> out a sensible format for that.

Having three flags to track the fp state and then a bunch of WARN()s
checking for invalid combinations is quite brittle, so any documentation
that can help to justify this would certainly be useful!

I've left a couple of comments on some of the patches, but it looks like
Dave was reviewing them but stopped short of the meat and potatoes in the
last two patches. I'd like to see his Ack on those before picking them up,
as well as testing from somebody with hardware because this is _very_
subtle stuff.

Is it worth me picking some of the preparatory patches up on their own?



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