Re: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers

From: Catalin Marinas
Date: Wed Nov 30 2016 - 06:32:09 EST


On Wed, Nov 30, 2016 at 04:44:52PM +0530, Siddhesh Poyarekar wrote:
> On Thursday 24 November 2016 07:10 PM, Suzuki K Poulose wrote:
> > + d) CPU Identification :
> > + MIDR_EL1 is exposed to help identify the processor. On a
> > + heterogeneous system, this could be racy (just like getcpu()). The
> > + process could be migrated to another CPU by the time it uses the
> > + register value, unless the CPU affinity is set. Hence, there is no
> > + guarantee that the value reflects the processor that it is
> > + currently executing on. The REVIDR is not exposed due to this
> > + constraint, as REVIDR makes sense only in conjunction with the
> > + MIDR. Alternately, MIDR_EL1 and REVIDR_EL1 are exposed via sysfs
> > + at:
> > +
> > + /sys/devices/system/cpu/cpu$ID/regs/identification/
> > + \- midr
> > + \- revidr
> > +
>
> This doesn't seem to be implemented in this patchset.

No. However, we merged the functionality above already and forgot about
the documentation part, so we just clarify it now.

--
Catalin