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Tsirkin" To: Guenter Roeck Subject: Re: [PATCH] virtio_net: Revert "virtio_net: set the default max ring size by find_vqs()" Message-ID: <20220815164013-mutt-send-email-mst@kernel.org> References: <20220815090521.127607-1-mst@redhat.com> <20220815203426.GA509309@roeck-us.net> MIME-Version: 1.0 In-Reply-To: <20220815203426.GA509309@roeck-us.net> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Jens Axboe , "Martin K. Petersen" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, James Bottomley , Linus Torvalds , Eric Dumazet , Greg KH , c@redhat.com, Jakub Kicinski , Paolo Abeni , Andres Freund , "David S. Miller" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Mon, Aug 15, 2022 at 01:34:26PM -0700, Guenter Roeck wrote: > On Mon, Aug 15, 2022 at 05:16:50AM -0400, Michael S. Tsirkin wrote: > > This reverts commit 762faee5a2678559d3dc09d95f8f2c54cd0466a7. > > > > This has been reported to trip up guests on GCP (Google Cloud). Why is > > not yet clear - to be debugged, but the patch itself has several other > > issues: > > > > - It treats unknown speed as < 10G > > - It leaves userspace no way to find out the ring size set by hypervisor > > - It tests speed when link is down > > - It ignores the virtio spec advice: > > Both \field{speed} and \field{duplex} can change, thus the driver > > is expected to re-read these values after receiving a > > configuration change notification. > > - It is not clear the performance impact has been tested properly > > > > Revert the patch for now. > > > > Link: https://lore.kernel.org/r/20220814212610.GA3690074%40roeck-us.net > > Link: https://lore.kernel.org/r/20220815070203.plwjx7b3cyugpdt7%40awork3.anarazel.de > > Link: https://lore.kernel.org/r/3df6bb82-1951-455d-a768-e9e1513eb667%40www.fastmail.com > > Link: https://lore.kernel.org/r/FCDC5DDE-3CDD-4B8A-916F-CA7D87B547CE%40anarazel.de > > Fixes: 762faee5a267 ("virtio_net: set the default max ring size by find_vqs()") > > Cc: Xuan Zhuo > > Cc: Jason Wang > > Signed-off-by: Michael S. Tsirkin > > Tested-by: Andres Freund > > I ran this patch through a total of 14 syskaller tests, 2 test runs each on > 7 different crashes reported by syzkaller (as reported to the linux-kernel > mailing list). No problems were reported. I also ran a single cross-check > with one of the syzkaller runs on top of v6.0-rc1, without this patch. > That test run failed. > > Overall, I think we can call this fixed. > > Guenter It's more of a work around though since we don't yet have the root cause for this. I suspect a GCP hypervisor bug at the moment. This is excercising a path we previously only took on GFP_KERNEL allocation failures during probe, I don't think that happens a lot. -- MST _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization