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

Alex Bennée
2017-10-30T16:12:13Z

Dave Martin <Dave.Martin@arm.com> writes:

> 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.

Ahh probably those. It was only a few header file shuffles. I was
rushing to apply before my flight back I failed to note the change in
base commit.

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

Only that #endif _ASM_ had been dropped from the header file.

>
> Cheers
> ---Dave