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bh=GmElzA9wpYCBzsDOe8cwU9sQH0JD1wOish4AaZbWI0I=; b=FAt1PuPpIBFcXVZiYVaPhRtkJP 5G+1JTMZ8vrbWxxA1KFItn+Inf5DBoLQ9lrbYGCgOpPAwQEn0dBMz8cS6DsKxm7M2+3D01ZZzYl4Z QKOUPlpEta6BMePXTMB0XmVRptmDOFlcemWVqVuvB4JlTFgzs23RW/UGWu3m7yunpgVk=; Received: from [95.248.141.113] (port=62022 helo=bywater) by esm19.siteground.biz with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.98.1) (envelope-from ) id 1vZ9R3-00000000Mx9-3X9B; Fri, 26 Dec 2025 15:08:57 +0000 Date: Fri, 26 Dec 2025 16:08:56 +0100 From: Francesco Valla To: Matias Ezequiel Vara Larsen Cc: Marc Kleine-Budde , Vincent Mailhol , Harald Mommer , Mikhail Golubev-Ciuchea , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , linux-can@vger.kernel.org, virtualization@lists.linux.dev, Wolfgang Grandegger , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Stefano Garzarella Subject: Re: [PATCH v6] can: virtio: Add virtio CAN driver Message-ID: References: Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Description:  Content-Disposition: inline In-Reply-To: X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - esm19.siteground.biz X-AntiAbuse: Original Domain - lists.linux.dev X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - valla.it X-Source: X-Source-Args: X-Source-Dir: X-SGantispam-id: 6fc56d8cb4eb9f5d796ae3035ac3e414 AntiSpam-DLS: false AntiSpam-DLSP: AntiSpam-DLSRS: AntiSpam-TS: 1.0 CFBL-Address: feedback@antispam.mailspamprotection.com; report=arf CFBL-Feedback-ID: 1vZ9RI-0000000CcNX-25SD-feedback@antispam.mailspamprotection.com Authentication-Results: outgoing.instance-europe-west4-mxlq.prod.antispam.mailspamprotection.com; iprev=pass (214.173.214.35.bc.googleusercontent.com) smtp.remote-ip=35.214.173.214; auth=pass (LOGIN) smtp.auth=esm19.siteground.biz; dkim=pass header.d=valla.it header.s=default header.a=rsa-sha256; arc=none Hi, On Sun, Dec 14, 2025 at 04:25:54PM +0100, Francesco Valla wrote: > While stress testing this, I noticed that flooding the virtio-can > interface with packets leads to an hang of the interface itself. > I am seeing this issuing, at host side: > > while true; do cansend can0 123#00; done > > with: > > - QEMU: the tip of the master branch plus [2] > - vhost-device: the tip of the main branch > > and the following QEMU invocation: > > qemu-system-x86_64 -serial mon:stdio \ > -m 2G -smp 2 \ > -kernel $(pwd)/BUILD.bin/arch/x86/boot/bzImage \ > -initrd /home/francesco/SRC/LINUX_KERNEL/initramfs.gz \ > -append "loglevel=7 console=ttyS0" \ > -machine memory-backend=pc.ram \ > -object memory-backend-file,id=pc.ram,size=2G,mem-path=/tmp/pc.ram,share=on \ > -chardev socket,id=can0,path=/tmp/sock-can0 \ > -device vhost-user-can-pci,chardev=can0 > > > Restarting the interface (i.e.: ip link set down and the up) does not > fix the situation. > > I'll try to do some more testing during the next days. After a deep dive, I _think_ the problem actually lies in vhost-device, since it is not there (or al least, it seems so) using an alternative implementation that uses the qemu socketcan support [0] (implementation which builds on top of the work done by Harald and Mikhail): qemu-system-x86_64 -serial mon:stdio \ -m 2G -smp 2 -enable-kvm \ -kernel $(pwd)/BUILD.bin/arch/x86/boot/bzImage \ -initrd /home/francesco/SRC/LINUX_KERNEL/initramfs.gz \ -append "loglevel=7 console=ttyS0" \ -object can-bus,id=canbus0 -object can-host-socketcan,id=canhost0,if=vcan0,canbus=canbus0 \ -device virtio-can-pci,canbus=canbus0 Unfortunately, my Rust knoweledge is not sufficient to understand the vhost-device implementation [1]; the issue seems to be related to the host->guest vring becoming empty and not refilling anymore. Regards, Francesco [0] https://github.com/WallaceIT/qemu/tree/virtio-can [1] https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-can