Re: git: c499ad6f997c - main - virtio: Use bus_dma for ring and indirect buffer allocations [Really: kernel: vtnet0: watchdog timeout on queue xx]

From: Mark Millard <marklmi_at_yahoo.com>
Date: Mon, 09 Mar 2026 02:40:19 UTC
On 3/8/26 10:39, Herbert J. Skuhra wrote:
> On Tue, 03 Mar 2026 18:37:57 +0100, Andrew Turner wrote:
>>
>> The branch main has been updated by andrew:
>>
>> URL: https://cgit.FreeBSD.org/src/commit/?id=c499ad6f997c8c5f61c88925e6d1e826d0c0f6c4
>>
>> commit c499ad6f997c8c5f61c88925e6d1e826d0c0f6c4
>> Author:     Sarah Walker <sarah.walker2@arm.com>
>> AuthorDate: 2026-03-03 16:08:11 +0000
>> Commit:     Andrew Turner <andrew@FreeBSD.org>
>> CommitDate: 2026-03-03 16:29:15 +0000
>>
>>     virtio: Use bus_dma for ring and indirect buffer allocations
>>     
>>     While the majority of virtio platforms will be fully coherent, some may
>>     require cache maintenance or other specific device memory handling (eg for
>>     secure partitioning). Using bus_dma allows for these usecases.
>>     
>>     The virtio buffers are marked as coherent; this should ensure that sync
>>     calls are no-ops in the common cases.
>>     
>>     Reviewed by:    andrew
>>     Sponsored by:   Arm Ltd
>>     Differential Revision:  https://reviews.freebsd.org/D54959
>> ---
>>  sys/dev/virtio/virtio_ring.h |  27 ++++--
>>  sys/dev/virtio/virtqueue.c   | 216 +++++++++++++++++++++++++++++++++++++------
>>  2 files changed, 209 insertions(+), 34 deletions(-)
> 
> After this change I see a lot of "kernel: vtnet0: watchdog timeout on
> queue xx" errors on amd64 (arm64 seems to be OK).

See below about other reports of the messages.

> 
> Reverting this commit resolves the issue.
> 
> 

freebsd-current has the following notes, implicitly referencing official
builders doing official builds:

QUOTE
On 3/8/26 17:10, Philip Paeps wrote:
> On 2026-03-08 07:10:01 (+0800), Michael Butler wrote:
>> Is anyone else seeing timeouts on virtual interfaces? e.g.
>>
>> Mar  7 15:00:27 george kernel: vtnet0: watchdog timeout on queue 0
>> Mar  7 15:00:45 george kernel: vtnet0: watchdog timeout on queue 0
>
> I started seeing these on today's build too.
>
> It seems to happen more or less randomly.  I can't point at anything
> specific that might be triggering it.
>
> Philip
>
>
END QUOTE

-- 
===
Mark Millard
marklmi at yahoo.com