This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH v2 26/28] arm64/sve: Add documentation
- From: Dave Martin <Dave dot Martin at arm dot com>
- To: Alex Bennée <alex dot bennee at linaro dot org>
- Cc: linux-arch at vger dot kernel dot org, Mark Rutland <mark dot rutland at arm dot com>, libc-alpha at sourceware dot org, Ard Biesheuvel <ard dot biesheuvel at linaro dot org>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, Catalin Marinas <catalin dot marinas at arm dot com>, Will Deacon <will dot deacon at arm dot com>, Richard Sandiford <richard dot sandiford at arm dot com>, nd at arm dot com, kvmarm at lists dot cs dot columbia dot edu, linux-arm-kernel at lists dot infradead dot org
- Date: Mon, 9 Oct 2017 10:49:32 +0100
- Subject: Re: [PATCH v2 26/28] arm64/sve: Add documentation
- Authentication-results: sourceware.org; auth=none
- References: <1504198860-12951-1-git-send-email-Dave.Martin@arm.com> <1504198860-12951-27-git-send-email-Dave.Martin@arm.com> <59D7A4AF.40408@arm.com> <20171006173715.GC3611@e103592.cambridge.arm.com> <878tgkbr6m.fsf@linaro.org>
On Mon, Oct 09, 2017 at 10:34:25AM +0100, Alex Bennée wrote:
>
> Dave Martin <Dave.Martin@arm.com> writes:
>
> > On Fri, Oct 06, 2017 at 04:43:43PM +0100, Szabolcs Nagy wrote:
> >> On 31/08/17 18:00, Dave Martin wrote:
> >> > +9. System runtime configuration
> >> > +--------------------------------
> >> > +
> >> > +* To mitigate the ABI impact of expansion of the signal frame, a policy
> >> > + mechanism is provided for administrators, distro maintainers and developers
> >> > + to set the default vector length for userspace processes:
> >> > +
> >> > +/proc/cpu/sve_default_vector_length
> >>
> >>
> >> elsewhere in the patch series i see
> >>
> >> /proc/sys/abi/sve_default_vector_length
> >>
> >> is this supposed to be the same?
> >
> > Good spot, thanks!
> >
> > /proc/cpu/ was the old location: they should both say /proc/abi/.
> > I'll fix it.
>
> Isn't /sys (or rather sysfs) the preferred location for modern control
> knobs that mirror the kernels object model or is SVE a special case for
> extending /proc?
I couldn't figure out which kernel object this maps to. There's no
device, no driver. This isn't even per-cpu.
sysctl is already used for similar knobs to this one, so I followed that
precedent -- though if someone argues strongly enough it could be
changed.
Are there already examples of arch controls like this in sysfs? I
wasn't aware of any, but I didn't look all that hard...
Cheers
---Dave