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Tue, 21 Jul 2020 12:02:40 -0400 (EDT) Received: by x220.qyliss.net (Postfix, from userid 1000) id 9541D2E6; Tue, 21 Jul 2020 16:02:38 +0000 (UTC) From: Alyssa Ross To: Stefan Hajnoczi Subject: Re: Testing the virtio-vhost-user QEMU patch In-Reply-To: <20200721083048.GB144170@stefanha-x1.localdomain> References: <87h7u1s5k1.fsf@alyssa.is> <20200721083048.GB144170@stefanha-x1.localdomain> Date: Tue, 21 Jul 2020 16:02:38 +0000 Message-ID: <87d04osvoh.fsf@alyssa.is> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=66.111.4.27; envelope-from=hi@alyssa.is; helo=out3-smtp.messagingengine.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 12:02:41 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nikos Dragazis , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Stefan Hajnoczi writes: > On Tue, Jul 21, 2020 at 07:14:38AM +0000, Alyssa Ross wrote: >> Hi -- I hope it's okay me reaching out like this. >> >> I've been trying to test out the virtio-vhost-user implementation that's >> been posted to this list a couple of times, but have been unable to get >> it to boot a kernel following the steps listed either on >> or >> . >> >> Specifically, the kernel appears to be unable to write to the >> virtio-vhost-user device's PCI registers. I've included the full panic >> output from the kernel at the end of this message. The panic is >> reproducible with two different kernels I tried (with different configs >> and versions). I tried both versions of the virtio-vhost-user I was >> able to find[1][2], and both exhibited the same behaviour. >> >> Is this a known issue? Am I doing something wrong? > > Hi, > Unfortunately I'm not sure what the issue is. This is an early > virtio-pci register access before a driver for any specific device type > (net, blk, vhost-user, etc) comes into play. > > Did you test the git trees linked below or did you rebase the commits > on top of your own QEMU tree? I tested the git trees. For your one I had to make a slight modification to delete the memfd syscall wrapper in util/memfd.c, since it conflicted with the one that is now provided by Glibc. Nikos's tree I used totally unmodified. > Is your guest kernel a stock kernel.org/distro kernel or has it been > modified (especially with security patches)? I tried a slightly modified Chromium OS kernel (5.4.23), and a stock Ubuntu 18.10 kernel (4.15.0). I think the most "normal" setup I tried was building QEMU on Fedora 32, and then attempting to boot a freshly installed Ubuntu Server 18.10 VM with -chardev socket,id=chardev0,path=vhost-user.sock,server,nowait \ -device virtio-vhost-user-pci,chardev=chardev0 (The crash was reproducible with the full QEMU command lines in the write-ups, but these seemed to be the load-bearing bits.) > If no one else knows what is wrong here then it will be necessary to > check the Intel manuals to figure out the exact meaning of > "error_code(0x000b) - reserved bit violation" and why Linux triggers it > with "PGD 3b128067 P4D 3b128067 PUD 3b129067 PMD 3b12a067 PTE > 8000002000000073". Thanks for your insight. Now I at least have a place to start if nobody else knows what's up. :)