On 26.09.23 15:04, Michael Roth wrote:

On Sun, Sep 03, 2023 at 06:13:38PM -0400, Michael S. Tsirkin wrote:

quoted

      virtio_net: merge dma operations when filling mergeable buffers

This ^ patch (upstream commit 295525e29a) seems to cause a
network-related regression when using SWIOTLB in the guest. I noticed
this initially testing SEV guests, which use SWIOTLB by default, but
it can also be seen with normal guests when forcing SWIOTLB via
swiotlb=force kernel cmdline option. I see it with both 6.6-rc1 and
6.6-rc2 (haven't tried rc3 yet, but don't see any related changes
there), and reverting 714073495f seems to avoid the issue.

Steps to reproduce:

quoted

[...]

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced 295525e29a
#regzbot title virtio: network-related regression when using SWIOTLB in
the guest
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply and tell me -- ideally
while also telling regzbot about it, as explained by the page listed in
the footer of this mail.

Developers: When fixing the issue, remember to add 'Link:' tags pointing
to the report (the parent of this mail). See page linked in footer for
details.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
That page also explains what to do if mails like this annoy you.