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Date:   Fri, 29 Sep 2023 13:12:23 +0200
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Subject: Re: [GIT PULL] virtio: features
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From:   "Linux regression tracking #update (Thorsten Leemhuis)" 
        <regressions@leemhuis.info>
To:     Linux kernel regressions list <regressions@lists.linux.dev>
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        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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On 27.09.23 15:18, Linux regression tracking #adding (Thorsten Leemhuis)
wrote:
> On 26.09.23 15:04, Michael Roth wrote:
>> On Sun, Sep 03, 2023 at 06:13:38PM -0400, Michael S. Tsirkin wrote:
>>>       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:
>>> [...]
> 
> 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

Regzbot missed the fix due to a fluke:

#regzbot monitor:
https://lore.kernel.org/all/20230927055246.121544-1-xuanzhuo@linux.alibaba.com/
#regzbot fix: virtio_net: fix the missing of the dma cpu sync
#regzbot ignore-activity

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.