On 26.02.24 05:09, Peng Fan wrote: > Hi Oleksandr,
Hello Peng [snip] >> >> ... Peng, we have vhost-vsock (and vhost-net) Xen PoC. Although it is >> non- >> upstreamable in its current shape (based on old Linux version, requires some >> rework and proper integration, most likely requires involving Qemu and >> protocol changes to pass an additional info to vhost), it works with Linux >> v5.10 + patched Qemu v7.0, so you can refer to the Yocto meta layer which >> contains kernel patches for the details [1]. > > Thanks for the pointer, I am reading the code. > >> >> In a nutshell, before accessing the guest data the host module needs to map >> descriptors in virtio rings which contain either guest grant based DMA >> addresses (by using Xen grant mappings) or guest pseudo-physical addresses >> (by using Xen foreign mappings). After accessing the guest data the host >> module needs to unmap them. > > Ok, I thought the current xen virtio code already map every ready. > It does, as you said the virtio-blk-pci worked in your environment. But vhost(-vsock) is a special case, unlike for virtio-blk-pci where the whole backend resides in Qemu, here we have a split model. As I understand the Qemu performs only initial setup/configuration then offloads the I/O processing to a separate entity which is the Linux module in that particular case.
