On Monday, August 21, 2023 9:34:52 AM EDT Jocelyn Falempe wrote: > On 13/08/2023 04:20, nerdopolis wrote: > > On Wednesday, August 9, 2023 3:17:27 PM 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 the drm_client API. > >> This implementation with the drm client API, allocates new framebuffers, and looks a bit too complex to run in a panic handler. > >> Maybe we should add an API to "steal" the current framebuffer instead, because in a panic handler user-space is already stopped. > >> > >> To test it, make sure you're using the simpledrm driver, and trigger a panic: > >> echo c > /proc/sysrq-trigger > >> > >> There is one thing I don't know how to do, is to unregister the drm_panic when the graphic driver is unloaded. > >> drm_client_register() says it will automatically unregister on driver unload. But then I don't know how to remove it from my linked list, and free the drm_client_dev struct. > >> > >> This is a first draft, so let me know what do you think about it. > > Hi, > > > > Oh wow, that's my post. I'm sorry about the late reply, I only saw this late yesterday, and I wanted to test it first. > > I had to edit my test QEMU script a bit to use TianoCore for virtual UEFI boot as there is no gfxmode=keep for SimpleDRM to work otherwise when specifying -kernel to qemu AFAIK > > > > I tested it, and it works! That's pretty cool, although is it possible to show the message, such as "attempted to kill init"? > > Thanks for taking time to test it. Yes it's possible to show the panic > reason, as it's a parameter in the panic callback. > > > > I like the little ASCII Tux. Maybe an ASCII /!\ or [X] on the belly would make it more obvious to users that it is an error condition. > > Especially for non-English speaking users > > That's a good idea. It's also probably possible to re-use the tux boot > logo, but I didn't try it yet. > > But currently, my priority is to see if it can get accepted, and if it > can work with a wide range of drivers. > Alright, that makes sense. I don't have a huge variety of hardware, but I have a udl (displaylink 2) device that can be tested once ready > > > > > > I will tweak my script a bit so I can test it more quickly in the future too. > > > Best Regards, > > > > > Thanks! > >> > >> 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 | 286 +++++++++++++++++++++++++++++++ > >> drivers/gpu/drm/tiny/simpledrm.c | 2 + > >> include/drm/drm_panic.h | 26 +++ > >> 6 files changed, 329 insertions(+) > >> create mode 100644 drivers/gpu/drm/drm_panic.c > >> create mode 100644 include/drm/drm_panic.h > >> > >> > >> base-commit: 6995e2de6891c724bfeb2db33d7b87775f913ad1 > >> > > > > > > > > > > >
