Re: [PATCH v4 20/28] arm64/sve: Add prctl controls for userspace vector length management

Dave Martin
2017-10-28T16:05:09Z

On Fri, Oct 27, 2017 at 06:52:50PM +0100, Alex Bennée wrote:
>
> Dave Martin <Dave.Martin@arm.com> writes:
>
> > This patch adds two arm64-specific prctls, to permit userspace to
> > control its vector length:
> >
> > * PR_SVE_SET_VL: set the thread's SVE vector length and vector
> > length inheritance mode.
> >
> > * PR_SVE_GET_VL: get the same information.
> >
> > Although these prctls resemble instruction set features in the SVE
> > architecture, they provide additional control: the vector length
> > inheritance mode is Linux-specific and nothing to do with the
> > architecture, and the architecture does not permit EL0 to set its
> > own vector length directly. Both can be used in portable tools
> > without requiring the use of SVE instructions.
> >
> > Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Alex Bennée <alex.bennee@linaro.org>
>
> FYI there is a minor conflict applying this on current master.

There are some trivial conflicts with one or two patches that already
went into arm64/for-next/core, so I based on that for this posting, not
torvalds/master.

There's a note in the cover letter giving the precise commit I based
on, though the branch doesn't seem to have moved yet since I posted.

Otherwise, I don't see any conflict -- can you give details?

Cheers
---Dave