Re: [PATCH] arm64/sve: Lower the maximum allocation for the SVE ptrace regset

[Mark Brown]

On Wed, Feb 07, 2024 at 01:51:42PM +0000, Dave Martin wrote:
> On Wed, Feb 07, 2024 at 01:09:51PM +0000, Mark Brown wrote:

> > I think if we fix the ptrace regset issue we're doing a good enough job
> > of just using fully dynamic sizing with no limits other than what's been
> > enumerated there.  We could possibly deal with the enumberation code by
> > changing it to use ZCR/SMCR_ELx_LEN_ based defines so that it's
> > obviously coming from what we can possibly write to the register but
> > it's a bit less clear how to do that neatly.

> OK, but we still seem to have two competing approaches: clamp SVE_VQ_MAX
> for kernel internal purposes, or restore the dynamic sizing of
> NT_ARM_SVE based on the new regset core behaviour.

> Are you saying we should or both, or otherwise which one?

I'd like to remove uses of SVE_VQ_MAX, to the extent possible by making
things dynamic but if not by not using it I would like to not use
SVE_VQ_MAX partly due to the considerations you mentioned about people
picking up from looking at the kernel source that it's a good idea.

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