From: rishabhb@codeaurora.org
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org,
tsoni@codeaurora.org, psodagud@codeaurora.org,
sidgup@codeaurora.org, linux-remoteproc-owner@vger.kernel.org,
kernel-team@android.com
Subject: Re: [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs
Date: Wed, 9 Sep 2020 22:08:38 +0000 [thread overview]
Message-ID: <0101017474e9e04f-826f6c7b-d6cd-4654-a14b-c54eb6aaf351-000000@us-west-2.amazonses.com> (raw)
In-Reply-To: <0101017473e8b87b-d40d1102-822a-4791-9f49-5d8e0d5d9753-000000@us-west-2.amazonses.com>
+android kernel team
On 2020-09-09 10:27, rishabhb@codeaurora.org wrote:
> On 2020-09-04 15:02, Mathieu Poirier wrote:
>> On Thu, Sep 03, 2020 at 06:59:44PM -0500, Bjorn Andersson wrote:
>>> On Tue 01 Sep 17:05 CDT 2020, Mathieu Poirier wrote:
>>>
>>> > Hi Rishabh,
>>> >
>>> > On Thu, Aug 27, 2020 at 12:48:48PM -0700, Rishabh Bhatnagar wrote:
>>> > > From Android R onwards Google has restricted access to debugfs in user
>>> > > and user-debug builds. This restricts access to most of the features
>>> > > exposed through debugfs. This patch series adds a configurable option
>>> > > to move the recovery/coredump interfaces to sysfs. If the feature
>>> > > flag is selected it would move these interfaces to sysfs and remove
>>> > > the equivalent debugfs interface.
>>> >
>>> > What I meant wast to move the coredump entry from debugfs to sysfs and from
>>> > there make it available to user space using a kernel config.
>>>
>>> Why would we not always make this available in sysfs?
>>
>> At this time the options are in debugfs and vendors can decide to make
>> that
>> available on products if they want to. The idea behind using a kernel
>> configuration once moved to sysfs was to give the same kind of
>> options.
>>
>>>
>>> > But thinking further on this it may be better to simply provide an API
>>> > to set the coredump mode from the platform driver, the same way
>>> > rproc_coredump_set_elf_info() works.
>>>
>>> Being able to invoke these from the platform drivers sounds like a
>>> new
>>> feature. What would trigger the platform drivers to call this? Or are
>>> you perhaps asking for the means of the drivers to be able to select
>>> the
>>> default mode?
>>
>> My ultimate goal is to avoid needlessly stuffing things in sysfs. My
>> hope in
>> suggesting a new API was that platform drivers could recognise the
>> kind of
>> build/environment they operate in and setup the coredump mode
>> accordingly. That
>> would have allowed us to leave debugfs options alone.
>>
>>>
>>> Regarding the default mode, I think it would make sense to make the
>>> default "disabled", because this is the most sensible configuration
>>> in a
>>> "production" environment. And the sysfs means we have a convenient
>>> mechanism to configure it, even on production environments.
>>>
>>
>> I am weary of changing something that hasn't been requested.
>>
>>> > That will prevent breaking a fair amount of user space code...
>>> >
>>>
>>> We typically don't guarantee that the debugfs interfaces are stable
>>> and
>>> if I understand the beginning of you reply you still want to move it
>>> from debugfs to sysfs - which I presume would break such scripts in
>>> the
>>> first place?
>>
>> Correct - I am sure that moving coredump and recovery options to sysfs
>> will
>> break user space scripts. Even if debugfs is not part of the ABI it
>> would be
>> nice to avoid disrupting people as much as possible.
>>
>>>
>>>
>>> I would prefer to see that we don't introduce config options for
>>> every
>>> little thing, unless there's good reason for it.
>>
>> I totally agree. It is with great reluctance that I asked Rishab to
>> proceed
>> the way he did in V3. His usecase makes sense... On the flip side
>> this is
>> pushed down on the kernel community and I really like Christoph's
>> position about
>> fixing Android and leaving the kernel alone.
>>
> Well, removing debugfs is conscious decision taken by android due to
> security
> concerns and there is not we can fix there.
> Would it be a terrible idea to have recovery and coredump exposed from
> both
> sysfs and debugfs instead of choosing one and breaking userspace code?
>>>
>>> Regards,
>>> Bjorn
>>>
>>> > Let me know if that can work for you.
>>> >
>>> > Thanks,
>>> > Mathieu
>>> >
>>> > > 'Coredump' and 'Recovery' are critical
>>> > > interfaces that are required for remoteproc to work on Qualcomm Chipsets.
>>> > > Coredump configuration needs to be set to "inline" in debug/test build
>>> > > and "disabled" in production builds. Whereas recovery needs to be
>>> > > "disabled" for debugging purposes and "enabled" on production builds.
>>> > >
>>> > > Changelog:
>>> > >
>>> > > v1 -> v2:
>>> > > - Correct the contact name in the sysfs documentation.
>>> > > - Remove the redundant write documentation for coredump/recovery sysfs
>>> > > - Add a feature flag to make this interface switch configurable.
>>> > >
>>> > > Rishabh Bhatnagar (3):
>>> > > remoteproc: Expose remoteproc configuration through sysfs
>>> > > remoteproc: Add coredump configuration to sysfs
>>> > > remoteproc: Add recovery configuration to sysfs
>>> > >
>>> > > Documentation/ABI/testing/sysfs-class-remoteproc | 44 ++++++++
>>> > > drivers/remoteproc/Kconfig | 12 +++
>>> > > drivers/remoteproc/remoteproc_debugfs.c | 10 +-
>>> > > drivers/remoteproc/remoteproc_sysfs.c | 126 +++++++++++++++++++++++
>>> > > 4 files changed, 190 insertions(+), 2 deletions(-)
>>> > >
>>> > > --
>>> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>>> > > a Linux Foundation Collaborative Project
>>> > >
next prev parent reply other threads:[~2020-09-09 22:08 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 19:48 [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs Rishabh Bhatnagar
2020-08-27 19:48 ` [PATCH v2 1/3] remoteproc: Expose remoteproc configuration through sysfs Rishabh Bhatnagar
2020-08-27 19:48 ` [PATCH v2 2/3] remoteproc: Add coredump configuration to sysfs Rishabh Bhatnagar
2020-09-10 17:58 ` Greg KH
2020-08-27 19:48 ` [PATCH v2 3/3] remoteproc: Add recovery " Rishabh Bhatnagar
2020-09-01 22:05 ` [PATCH v2 0/3] Expose recovery/coredump configuration from sysfs Mathieu Poirier
2020-09-02 23:14 ` rishabhb
2020-09-03 19:45 ` Mathieu Poirier
2020-09-03 23:59 ` Bjorn Andersson
2020-09-04 22:02 ` Mathieu Poirier
2020-09-09 17:27 ` rishabhb
2020-09-09 22:08 ` rishabhb [this message]
[not found] ` <0101017473e8b9f1-9c800bfd-d724-473f-96b8-c43920cc8967-000000@us-west-2.amazonses.com>
2020-09-10 17:46 ` Mathieu Poirier
2020-09-10 17:59 ` Greg KH
2020-09-15 9:51 ` Arnaud POULIQUEN
2020-09-26 3:31 ` Bjorn Andersson
2020-09-29 7:43 ` Arnaud POULIQUEN
2020-10-14 0:32 ` Bjorn Andersson
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