Re: upstream kernel crashes

On Mon, Aug 15, 2022 at 01:34:41AM -0700, Andres Freund wrote:

Hi, 

On August 15, 2022 1:28:29 AM PDT, "Michael S. Tsirkin" [off-list ref] wrote:

quoted

On Mon, Aug 15, 2022 at 01:15:27AM -0700, Andres Freund wrote:

quoted

Hi,

On 2022-08-15 03:51:34 -0400, Michael S. Tsirkin wrote:

quoted

It is possible that GCP gets confused if ring size is smaller than the
device maximum simply because no one did it in the past.

So I pushed just the revert of 762faee5a267 to the test branch.
Could you give it a spin?

Seems to fix the issue, at least to the extent I can determine at 1am... :)

Greetings,

Andres Freund

So you tested this:

commit 13df5a7eaeb22561d39354b576bc98a7e2c389f9 (HEAD, kernel.org/test)
Author: Michael S. Tsirkin [off-list ref]
Date:   Mon Aug 15 03:44:38 2022 -0400

   Revert "virtio_net: set the default max ring size by find_vqs()"
   
   This reverts commit 762faee5a2678559d3dc09d95f8f2c54cd0466a7.
   
   Signed-off-by: Michael S. Tsirkin [off-list ref]

and it fixes both issues right? No crashes no networking issue?

Correct. I only did limited testing, but it's survived far longer / more reboots than anything since the commit.

Andres
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

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!

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index f7965c5dd36b..bdd5f481570b 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c

@@ -314,6 +314,9 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	if (!size || size > num)
 		size = num;
 
+	if (size > 1024)
+		size = 1024;
+
 	if (size & (size - 1)) {
 		dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", size);
 		return ERR_PTR(-EINVAL);

-- 
MST

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