Messages in this thread | | | From | Marc Zyngier <> | Subject | Re: [PATCH/RFC] arm64: pmu: add Qualcomm Technologies extensions | Date | Fri, 03 Mar 2017 10:17:28 +0000 |
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On Thu, Mar 02 2017 at 7:30:53 pm GMT, "Leeder, Neil" <nleeder@codeaurora.org> wrote: > Hi Mark Z., > > On 3/2/2017 4:05 AM, Marc Zyngier wrote: >> On 01/03/17 21:36, Leeder, Neil wrote: >>> On 3/1/2017 1:10 PM, Mark Rutland wrote: >>>> KVM already has (architected) PMU support, and without a corresponding >>>> KVM patch this is at best insufficient. I don't imagine the KVM folk >>>> will be too thrilled about the prospect of emulating an IMPLEMENTATION >>>> DEFINED CPU feature like this. >>> >>> Does KVM handle ARMv7 PMU implementations? If so, do you know what it >>> does for the scorpion_* and krait_* implementations in >>> arch/arm/kernel/perf_events_v7.c? These extensions in ARMv8 are very >>> similar to the krait extensions, with some 64-bit tweaks, so could be >>> handled by KVM the same way it handles the ARMv7 cases. >> >> No, KVM doesn't handle the ARMv7 PMU at all. I'm not aware of the >> virtualization extensions being available on Scorpion or Krait, which >> makes it a moot point. What it handles is the PMUv3 architecture. > > Thank you for the explanation. > > This driver is specifically for Qualcomm Technologies server > chips. They will not be in a heterogenous environment with > non-Qualcomm processors, so there should be no migration issues.
How do you know that? I'm afraid this is not something you or I can guarantee (and even less enforce).
> If we were to provide a patch which added KVM support for the 4 > additional registers here, would you consider reviewing it, or is > adding implementation-defined registers a show-stopper?
At the moment, it seems that there is a consensus against adding support for an IMPDEF PMU.
Thanks,
M. -- Jazz is not dead, it just smell funny.
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