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Fri, 16 Oct 2020 02:24:55 -0700 (PDT) Date: Fri, 16 Oct 2020 17:24:50 +0800 From: Leo Yan To: Sai Prakash Ranjan Subject: Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing Message-ID: <20201016092450.GG4646@leoy-ThinkPad-X240s> References: <20201015124522.1876-1-saiprakash.ranjan@codeaurora.org> <20201015160257.GA1450102@xps15> <20201016072401.GC4646@leoy-ThinkPad-X240s> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201016_052500_194526_2959AD16 X-CRM114-Status: GOOD ( 17.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Denis Nikitin , Mathieu Poirier , Suzuki K Poulose , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-kernel@lists.infradead.org, Mike Leach Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Sai, On Fri, Oct 16, 2020 at 02:10:47PM +0530, Sai Prakash Ranjan wrote: > Hi Leo, > > On 2020-10-16 12:54, Leo Yan wrote: > > On Thu, Oct 15, 2020 at 11:40:05PM -0700, Denis Nikitin wrote: > > > Hi Mathieu, > > > > > > I think one of the use cases could be VMs. > > > Is there isolation between EL1 guest kernels which we can control > > > from perf > > > in a system wide mode? > > > > Sorry for suddenly jumping in. > > > > For KVM, I think we need to implement mechanism for saving/restoring > > CoreSight context for every guest OS, the CPU PMUs has implemented > > related features [1]. > > > > Thanks, > > Leo > > > > [1] > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kvm/pmu.c > > > > What happens to the sysfs mode of tracing? For that we would still > need a config right to exclude kernel mode tracing completely. IIUC, sysfs mode and perf mode both can apply the same approach, the guest OS runs a thread context for the host, so when a guest OS is switched in or out, the hypervisor can save/restore the context for the guest OS; thus every guest OS will have its dedicated context and trace data ideally. Thanks, Leo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel