| Message ID | 20230915083307.1185571-1-jfalempe@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | drm/panic: Add a drm panic handler | expand |
On Friday, September 15, 2023 4:28:20 AM EDT Jocelyn Falempe wrote: > This introduces a new drm panic handler, which displays a message when a panic occurs. > So when fbcon is disabled, you can still see a kernel panic. > > This is one of the missing feature, when disabling VT/fbcon in the kernel: > https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/ > Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel. > > This is a proof of concept, and works only with simpledrm, using a new get_scanout_buffer() api > > To test it, make sure you're using the simpledrm driver, and trigger a panic: > echo c > /proc/sysrq-trigger > This seems to work pretty good! With this one, I don't need to have Weston (or another display server) running for it to work this time. The panic reason works, which is pretty sweet. FYI: I do get a hunk that fails to apply in simpledrm_remove in drivers/gpu/drm/tiny/simpledrm.c Seems to be a change in a recentish commit https://github.com/torvalds/linux/commit/84e6da7ad5537826343636b846530ec2167d4a19 Thanks! > v2 > * Use get_scanout_buffer() instead of the drm client API. (Thomas Zimmermann) > * Add the panic reason to the panic message (Nerdopolis) > * Add an exclamation mark (Nerdopolis) > > I didn't reuse the fbdev functions yet, that would need some fbdev refactoring, because they rely on struct fb_info, and struct vc_data (for font/console). But I still plan to at least try it for v3. > > A few more though: > 1) what about gpu with multiple monitor connected ? > maybe get_scanout_buffer() could return a list of scanout buffers ? > 2) I think for some GPU drivers, there might need a flush_scanout_buffer() function, that should be called after the scanout buffer has been filled ? > > Best regards, > > Jocelyn Falempe (2): > drm/panic: Add a drm panic handler > drm/simpledrm: Add drm_panic support > > drivers/gpu/drm/Kconfig | 11 ++ > drivers/gpu/drm/Makefile | 1 + > drivers/gpu/drm/drm_drv.c | 3 + > drivers/gpu/drm/drm_panic.c | 270 +++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/simpledrm.c | 17 ++ > include/drm/drm_drv.h | 14 ++ > include/drm/drm_panic.h | 41 +++++ > 7 files changed, 357 insertions(+) > create mode 100644 drivers/gpu/drm/drm_panic.c > create mode 100644 include/drm/drm_panic.h > > > base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c >
On 16/09/2023 15:09, nerdopolis wrote: > On Friday, September 15, 2023 4:28:20 AM EDT Jocelyn Falempe wrote: >> This introduces a new drm panic handler, which displays a message when a panic occurs. >> So when fbcon is disabled, you can still see a kernel panic. >> >> This is one of the missing feature, when disabling VT/fbcon in the kernel: >> https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/ >> Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel. >> >> This is a proof of concept, and works only with simpledrm, using a new get_scanout_buffer() api >> >> To test it, make sure you're using the simpledrm driver, and trigger a panic: >> echo c > /proc/sysrq-trigger >> > This seems to work pretty good! With this one, I don't need to have Weston (or another display server) running for it to work this time. > The panic reason works, which is pretty sweet. Thanks for testing, that's really appreciated. > > FYI: I do get a hunk that fails to apply in simpledrm_remove in drivers/gpu/drm/tiny/simpledrm.c > Seems to be a change in a recentish commit > https://github.com/torvalds/linux/commit/84e6da7ad5537826343636b846530ec2167d4a19 Thanks for the head-up, when doing this RFC, I'm based on latest released version v6.5, to avoid having to rebase too often. When it's closer to merging, I will rebase to drm-misc-next. Best regards,
Hi, On 9/15/23 10:28, Jocelyn Falempe wrote: > This introduces a new drm panic handler, which displays a message when a panic occurs. > So when fbcon is disabled, you can still see a kernel panic. > > This is one of the missing feature, when disabling VT/fbcon in the kernel: > https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/ > Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel. > > This is a proof of concept, and works only with simpledrm, using a new get_scanout_buffer() api > There's a panic handling entry in Documentation/gpu/todo.rst pointing to some work done in this area. Noralf. > To test it, make sure you're using the simpledrm driver, and trigger a panic: > echo c > /proc/sysrq-trigger > > v2 > * Use get_scanout_buffer() instead of the drm client API. (Thomas Zimmermann) > * Add the panic reason to the panic message (Nerdopolis) > * Add an exclamation mark (Nerdopolis) > > I didn't reuse the fbdev functions yet, that would need some fbdev refactoring, because they rely on struct fb_info, and struct vc_data (for font/console). But I still plan to at least try it for v3. > > A few more though: > 1) what about gpu with multiple monitor connected ? > maybe get_scanout_buffer() could return a list of scanout buffers ? > 2) I think for some GPU drivers, there might need a flush_scanout_buffer() function, that should be called after the scanout buffer has been filled ? > > Best regards, > > Jocelyn Falempe (2): > drm/panic: Add a drm panic handler > drm/simpledrm: Add drm_panic support > > drivers/gpu/drm/Kconfig | 11 ++ > drivers/gpu/drm/Makefile | 1 + > drivers/gpu/drm/drm_drv.c | 3 + > drivers/gpu/drm/drm_panic.c | 270 +++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/simpledrm.c | 17 ++ > include/drm/drm_drv.h | 14 ++ > include/drm/drm_panic.h | 41 +++++ > 7 files changed, 357 insertions(+) > create mode 100644 drivers/gpu/drm/drm_panic.c > create mode 100644 include/drm/drm_panic.h > > > base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
On 19/09/2023 01:19, Noralf Trønnes wrote: > Hi, > > On 9/15/23 10:28, Jocelyn Falempe wrote: >> This introduces a new drm panic handler, which displays a message when a panic occurs. >> So when fbcon is disabled, you can still see a kernel panic. >> >> This is one of the missing feature, when disabling VT/fbcon in the kernel: >> https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/ >> Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel. >> >> This is a proof of concept, and works only with simpledrm, using a new get_scanout_buffer() api >> > > There's a panic handling entry in Documentation/gpu/todo.rst pointing to > some work done in this area. Thanks a lot for this pointer, I wasn't aware of this previous drm panic attempt. I hope this one will go a bit further ;) Also I wasn't sure about what is allowed or not in the panic handler, and this doc makes things really clear. Regarding the fbcon interactions, I prevent this at build time, I rely on userspace consoles, and hope they will progressively replace fbcon. My real question is how did I missed that ? My google-fu failed me this time. Best regards,