Em 03/05/2023 14:43, Timur Kristóf escreveu:
Hi Felix,
On Wed, 2023-05-03 at 11:08 -0400, Felix Kuehling wrote:
That's the worst-case scenario where you're debugging HW or FW
issues.
Those should be pretty rare post-bringup. But are there hangs caused
by
user mode driver or application bugs that are easier to debug and
probably don't even require a GPU reset?
There are many GPU hangs that gamers experience while playing. We have
dozens of open bug reports against RADV about GPU hangs on various GPU
generations. These usually fall into two categories:
1. When the hang always happens at the same point in a game. These are
painful to debug but manageable.
2. "Random" hangs that happen to users over the course of playing a
game for several hours. It is absolute hell to try to even reproduce
let alone diagnose these issues, and this is what we would like to
improve.
For these hard-to-diagnose problems, it is already a challenge to
determine whether the problem is the kernel (eg. setting wrong voltages
/ frequencies) or userspace (eg. missing some synchronization), can be
even a game bug that we need to work around.
For example most VM faults can
be handled without hanging the GPU. Similarly, a shader in an endless
loop should not require a full GPU reset.
This is actually not the case, AFAIK André's test case was an app that
had an infinite loop in a shader.
This is the test app if anyone want to try out:
https://github.com/andrealmeid/vulkan-triangle-v1. Just compile and run.
The kernel calls amdgpu_ring_soft_recovery() when I run my example, but
I'm not sure what a soft recovery means here and if it's a full GPU
reset or not.
But if we can at least trust the CP registers to dump information for
soft resets, it would be some improvement from the current state I think
It's more complicated for graphics because of the more complex
pipeline
and the lack of CWSR. But it should still be possible to do some
debugging without JTAG if the problem is in SW and not HW or FW. It's
probably worth improving that debugability without getting hung-up on
the worst case.
I agree, and we welcome any constructive suggestion to improve the
situation. It seems like our idea doesn't work if the kernel can't give
us the information we need.
How do we move forward?
Best regards,
Timur
