Re: [PATCH v5 00/17] Add Qualcomm Minidump kernel driver related support

From: Mukesh Ojha
Date: Mon Sep 11 2023 - 16:52:11 EST



On 9/11/2023 2:22 PM, Bagas Sanjaya wrote:
On Sun, Sep 10, 2023 at 01:46:01AM +0530, Mukesh Ojha wrote:
Hi All,

This is to continuation from the conversation happened at v4

https://lore.kernel.org/lkml/632c5b97-4a91-c3e8-1e6c-33d6c4f6454f@xxxxxxxxxxx/

https://lore.kernel.org/lkml/695133e6-105f-de2a-5559-555cea0a0462@xxxxxxxxxxx/

We have put abstract on LPC on this topic as well as initiated a mail thread
with other SoC vendors but did not get much traction on it.

https://lore.kernel.org/lkml/0199db00-1b1d-0c63-58ff-03efae02cb21@xxxxxxxxxxx/

We explored most of possiblity present in kernel to address this issue[1] but
solution like kdump/fadump does not seems safe/secure/performant from our
perspective.

Hence, with this series we tried to make the minidump kernel driver, simple
and tied with pstore frontends, so that it collects the present available
frontends data like dmesg, ftrace, pmsg, ftrace., Also, we will be working
towards enhancing generic pstore to capture more debug data which will be
helpful for first hand of debugging that can benefit both other pstore users
as well as us as minidump users.

One of the proposal made here,
https://lore.kernel.org/lkml/1683561060-2197-1-git-send-email-quic_mojha@xxxxxxxxxxx/

Looking forward for your comments.

Thanks,
Mukesh

[1]
Minidump is a best effort mechanism to collect useful and predefined data
for first level of debugging on end user devices running on Qualcomm SoCs.
It is built on the premise that System on Chip (SoC) or subsystem part of
SoC crashes, due to a range of hardware and software bugs. Hence, the
ability to collect accurate data is only a best-effort. The data collected
could be invalid or corrupted, data collection itself could fail, and so on.

Qualcomm devices in engineering mode provides a mechanism for generating
full system ramdumps for post mortem debugging. But in some cases it's
however not feasible to capture the entire content of RAM. The minidump
mechanism provides the means for selecting which snippets should be
included in the ramdump.

The core of SMEM based minidump feature is part of Qualcomm's boot
firmware code. It initializes shared memory (SMEM), which is a part of
DDR and allocates a small section of SMEM to minidump table i.e also
called global table of content (G-ToC). Each subsystem (APSS, ADSP, ...)
has their own table of segments to be included in the minidump and all
get their reference from G-ToC. Each segment/region has some details
like name, physical address and it's size etc. and it could be anywhere
scattered in the DDR.

Existing upstream Qualcomm remoteproc driver[1] already supports SMEM
based minidump feature for remoteproc instances like ADSP, MODEM, ...
where predefined selective segments of subsystem region can be dumped
as part of coredump collection which generates smaller size artifacts
compared to complete coredump of subsystem on crash.

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/remoteproc/qcom_common.c#n142

In addition to managing and querying the APSS minidump description,
the Linux driver maintains a ELF header in a segment. This segment
gets updated with section/program header whenever a new entry gets
registered.

Changes in v5:
- On suggestion from Pavan.k, to have single function call for minidump collection
from remoteproc driver, separated the logic to have separate minidump file called
qcom_rproc_minidump.c and also renamed the function from qcom_minidump() to
qcom_rproc_minidump(); however, dropped his suggestion about rework on lazy deletion
during region unregister in this series, will pursue it in next series.

- To simplify the minidump driver, removed the complication for frontend and different
backend from Greg suggestion, will pursue this once main driver gets mainlined.

- Move the dynamic ramoops region allocation from Device tree approach to command line
approch with the introduction command line parsing and memblock reservation during
early boot up; Not added documentation about it yet, will add if it gets positive
response.

- Exporting linux banner from kernel to make minidump build also as module, however,
minidump is a debug module and should be kernel built to get most debug information
from kernel.

- Tried to address comments given on dload patch series.

Changes in v4: https://lore.kernel.org/lkml/1687955688-20809-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Redesigned the driver and divided the driver into front end and backend (smem) so
that any new backend can be attached easily to avoid code duplication.
- Patch reordering as per the driver and subsystem to easier review of the code.
- Removed minidump specific code from remoteproc to minidump smem based driver.
- Enabled the all the driver as modules.
- Address comments made on documentation and yaml and Device tree file [Krzysztof/Konrad]
- Address comments made qcom_pstore_minidump driver and given its Device tree
same set of properties as ramoops. [Luca/Kees]
- Added patch for MAINTAINER file.
- Include defconfig change as one patch as per [Krzysztof] suggestion.
- Tried to remove the redundant file scope variables from the module as per [Krzysztof] suggestion.
- Addressed comments made on dload mode patch v6 version
https://lore.kernel.org/lkml/1680076012-10785-1-git-send-email-quic_mojha@xxxxxxxxxxx/

Changes in v3: https://lore.kernel.org/lkml/1683133352-10046-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Addressed most of the comments by Srini on v2 and refactored the minidump driver.
- Added platform device support
- Unregister region support.
- Added update region for clients.
- Added pending region support.
- Modified the documentation guide accordingly.
- Added qcom_pstore_ramdump client driver which happen to add ramoops platform
device and also registers ramoops region with minidump.
- Added download mode patch series with this minidump series.
https://lore.kernel.org/lkml/1680076012-10785-1-git-send-email-quic_mojha@xxxxxxxxxxx/

Changes in v2: https://lore.kernel.org/lkml/1679491817-2498-1-git-send-email-quic_mojha@xxxxxxxxxxx/
- Addressed review comment made by [quic_tsoni/bmasney] to add documentation.
- Addressed comments made by [srinivas.kandagatla]
- Dropped pstore 6/6 from the last series, till i get conclusion to get pstore
region in minidump.
- Fixed issue reported by kernel test robot.

Changes in v1: https://lore.kernel.org/lkml/1676978713-7394-1-git-send-email-quic_mojha@xxxxxxxxxxx/

Testing of the patches has been done on sm8450 target after enabling config like
CONFIG_PSTORE_RAM and CONFIG_PSTORE_CONSOLE and once the device boots up.

echo mini > /sys/module/qcom_scm/parameters/download_mode

Try crashing it via devmem2 0xf11c000(this is known to create xpu violation and
and put the device in download mode) on command prompt.

Default storage type is set to via USB, so minidump would be downloaded with the
help of x86_64 machine (running PCAT tool) attached to Qualcomm device which has
backed minidump boot firmware support.

This will make the device go to download mode and collect the minidump on to the
attached x86 machine running the Qualcomm PCAT tool(This comes as part Qualcomm
package manager kit).

After that we will see a bunch of predefined registered region as binary blobs files
starts with md_* downloaded on the x86 machine on given location in PCAT tool from
the target device, more about this can be found in qualcomm minidump guide patch.


I tried to apply this series on top of 535a265d7f0dd50 (as suggested by
`b4 am -l -g`), but it conflicts on patch [04/17]. Please specify the
exact base commit or another series for which this series is based on.

Apologies !
I just realized, it was 6.5-rc7, but let me rebase version of the series;

Sorry, for all the reviewed done so far, i will definitely take care of them or reply.

-Mukesh

Thanks.