Re: upstream kernel crashes

Hi,

On 2022-08-15 16:21:51 -0400, Michael S. Tsirkin wrote:

On Mon, Aug 15, 2022 at 10:46:17AM -0700, Andres Freund wrote:

quoted

Hi,

On 2022-08-15 12:50:52 -0400, Michael S. Tsirkin wrote:

quoted

On Mon, Aug 15, 2022 at 09:45:03AM -0700, Andres Freund wrote:

quoted

Hi,

On 2022-08-15 11:40:59 -0400, Michael S. Tsirkin wrote:

quoted

OK so this gives us a quick revert as a solution for now.
Next, I would appreciate it if you just try this simple hack.
If it crashes we either have a long standing problem in virtio
code or more likely a gcp bug where it can't handle smaller
rings than what device requestes.
Thanks!

I applied the below and the problem persists.

[...]

Okay!

Just checking - I applied and tested this atop 6.0-rc1, correct? Or did you
want me to test it with the 762faee5a267 reverted? I guess what you're trying
to test if a smaller queue than what's requested you'd want to do so without
the problematic patch applied...


Either way, I did this, and there are no issues that I could observe. No
oopses, no broken networking. But:

To make sure it does something I added a debugging printk - which doesn't show
up. I assume this is at a point at least earlyprintk should work (which I see
getting enabled via serial)?

Sorry if I was unclear.  I wanted to know whether the change somehow
exposes a driver bug or a GCP bug. So what I wanted to do is to test
this patch on top of *5.19*, not on top of the revert.

Right, the 5.19 part was clear, just the earlier test:

quoted

quoted

quoted

On 2022-08-15 11:40:59 -0400, Michael S. Tsirkin wrote:

quoted

OK so this gives us a quick revert as a solution for now.
Next, I would appreciate it if you just try this simple hack.
If it crashes we either have a long standing problem in virtio
code or more likely a gcp bug where it can't handle smaller
Thanks!

I wasn't sure about.

After I didn't see any effect on 5.19 + your patch, I grew a bit suspicious
and added the printks.

Yes I think printk should work here.

The reason the debug patch didn't change anything, and that my debug printk
didn't show, is that gcp uses the legacy paths...

If there were a bug in the legacy path, it'd explain why the problem only
shows on gcp, and not in other situations.

I'll queue testing the legacy path with the equivalent change.

- Andres


Greetings,

Andres Freund
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