On Wed, Dec 08, 2021 at 01:20:10PM +0800, Longpeng(Mike) wrote: > From: Longpeng <longpe...@huawei.com> > > Hi guys, > > This patch introduces vhost-vdpa-net device, which is inspired > by vhost-user-blk and the proposal of vhost-vdpa-blk device [1]. > > I've tested this patch on Huawei's offload card: > ./x86_64-softmmu/qemu-system-x86_64 \ > -device vhost-vdpa-net-pci,vdpa-dev=/dev/vhost-vdpa-0 > > For virtio hardware offloading, the most important requirement for us > is to support live migration between offloading cards from different > vendors, the combination of netdev and virtio-net seems too heavy, we > prefer a lightweight way. > > Maybe we could support both in the future ? Such as: > > * Lightweight > Net: vhost-vdpa-net > Storage: vhost-vdpa-blk > > * Heavy but more powerful > Net: netdev + virtio-net + vhost-vdpa > Storage: bdrv + virtio-blk + vhost-vdpa > > [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg797569.html
Stefano presented a plan for vdpa-blk at KVM Forum 2021: https://kvmforum2021.sched.com/event/ke3a/vdpa-blk-unified-hardware-and-software-offload-for-virtio-blk-stefano-garzarella-red-hat It's closer to today's virtio-net + vhost-net approach than the vhost-vdpa-blk device you have mentioned. The idea is to treat vDPA as an offload feature rather than a completely separate code path that needs to be maintained and tested. That way QEMU's block layer features and live migration work with vDPA devices and re-use the virtio-blk code. The key functionality that has not been implemented yet is a "fast path" mechanism that allows the QEMU virtio-blk device's virtqueue to be offloaded to vDPA. The unified vdpa-blk architecture should deliver the same performance as the vhost-vdpa-blk device you mentioned but with more features, so I wonder what aspects of the vhost-vdpa-blk idea are important to you? QEMU already has vhost-user-blk, which takes a similar approach as the vhost-vdpa-blk device you are proposing. I'm not against the vhost-vdpa-blk approach in priciple, but would like to understand your requirements and see if there is a way to collaborate on one vdpa-blk implementation instead of dividing our efforts between two. Stefan
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