From mboxrd@z Thu Jan 1 00:00:00 1970 From: nleeder@codeaurora.org (Leeder, Neil) Date: Thu, 2 Mar 2017 14:30:53 -0500 Subject: [PATCH/RFC] arm64: pmu: add Qualcomm Technologies extensions In-Reply-To: <4b90b76f-f08d-f248-8153-287b2552dceb@arm.com> References: <1488385085-19238-1-git-send-email-nleeder@codeaurora.org> <20170301181032.GL28874@leverpostej> <4b90b76f-f08d-f248-8153-287b2552dceb@arm.com> Message-ID: <2c6fcb54-482a-14dc-0fbb-58df0f9a68b5@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. 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? Thanks, Neil -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.