From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Leo Yan <leo.yan@linaro.org>
Cc: Denis Nikitin <denik@chromium.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org,
linux-kernel@vger.kernel.org, Stephen Boyd <swboyd@chromium.org>,
linux-arm-kernel@lists.infradead.org,
Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing
Date: Fri, 16 Oct 2020 16:00:46 +0530 [thread overview]
Message-ID: <f4fff311015e45214e07606fcf33e8e4@codeaurora.org> (raw)
In-Reply-To: <20201016092450.GG4646@leoy-ThinkPad-X240s>
Hi Leo,
On 2020-10-16 14:54, Leo Yan wrote:
> 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 for the explanation, so for this usecase then we would have to
implement something as you suggested, not sure how hard would that be
looking at my KVM knowledge(which at the moment is almost nil) when
compared to a kconfig ;)
Thanks,
Sai
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next prev parent reply other threads:[~2020-10-16 10:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 12:45 [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing Sai Prakash Ranjan
2020-10-15 14:27 ` Suzuki K Poulose
2020-10-16 8:30 ` Sai Prakash Ranjan
2020-10-15 16:02 ` Mathieu Poirier
[not found] ` <CADDJ8CXS8gGuXL45vR6xiHwJhZNcUJPvHMVYSGR6LDETRPJFiQ@mail.gmail.com>
2020-10-16 7:24 ` Leo Yan
2020-10-16 8:40 ` Sai Prakash Ranjan
2020-10-16 9:24 ` Leo Yan
2020-10-16 10:30 ` Sai Prakash Ranjan [this message]
2020-10-16 11:38 ` Suzuki Poulose
2020-10-16 13:14 ` Leo Yan
2020-10-16 13:17 ` Suzuki Poulose
2020-10-16 11:11 ` Suzuki Poulose
[not found] ` <dd400fd7017a5d92b55880cf28378267@codeaurora.org>
2021-01-18 14:47 ` Mattias Nissler
2021-01-18 20:23 ` Mathieu Poirier
[not found] ` <32216e9fa5c9ffb9df1123792d40eafb@codeaurora.org>
2021-01-19 8:36 ` Al Grant
[not found] ` <03b893801841f732a25072b4e62f8e0b@codeaurora.org>
2021-01-19 10:33 ` Suzuki K Poulose
2021-01-19 11:56 ` Al Grant
2021-01-20 18:48 ` Mathieu Poirier
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