On Mon, Oct 09, 2017 at 10:34:25AM +0100, Alex Benn?e wrote:

Dave Martin [off-list ref] writes:

quoted

On Fri, Oct 06, 2017 at 04:43:43PM +0100, Szabolcs Nagy wrote:

quoted

On 31/08/17 18:00, Dave Martin wrote:

quoted

+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