Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
Message-ID: <86d04b92-1b1e-4676-95e3-87e8e0082526@leemhuis.info>
Date:   Wed, 27 Sep 2023 15:18:29 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [GIT PULL] virtio: features
Content-Language: en-US, de-DE
To:     Michael Roth <michael.roth@amd.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        eperezma@redhat.com, jasowang@redhat.com, shannon.nelson@amd.com,
        xuanzhuo@linux.alibaba.com, yuanyaogoog@chromium.org,
        yuehaibing@huawei.com, Thomas Lendacky <thomas.lendacky@amd.com>
References: <20230903181338-mutt-send-email-mst@kernel.org>
 <20230926130451.axgodaa6tvwqs3ut@amd.com>
From:   "Linux regression tracking #adding (Thorsten Leemhuis)" 
        <regressions@leemhuis.info>
Reply-To: Linux regressions mailing list <regressions@lists.linux.dev>
In-Reply-To: <20230926130451.axgodaa6tvwqs3ut@amd.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

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

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.