> Subject: RE: question about virtio-vsock on xen > > On Mon, 26 Feb 2024, Peng Fan wrote: > > Hi Stefano, > > > > > Subject: Re: question about virtio-vsock on xen > > > > > > Hi Peng, > > > > > > We haven't tried to setup virtio-vsock yet. > > > > > > In general, I am very supportive of using QEMU for virtio backends. > > > We use QEMU to provide virtio-net, virtio-block, virtio-console and more. > > > > Would you mind share how to setup virtio-console using qemu + xen? > > Vikram (CCed) has been working on it and should be able to share more > details > > > > > However, typically virtio-vsock comes into play for VM-to-VM > > > communication, which is different. Going via QEMU in Dom0 just to > > > have 1 VM communicate with another VM is not an ideal design: it > > > adds latency and uses resources in Dom0 when actually we could do > without it. > > > > > > A better model for VM-to-VM communication would be to have the VM > > > talk to each other directly via grant table or pre-shared memory > > > (see the static shared memory feature) or via Xen hypercalls (see > > > Argo.) > > > > The goal is to make android trout VM run with XEN + i.MX95, so need vsock. > > I am not familiar with the details of Android Trout... Where is vsock used? > Just asking for my own understanding.
Here is the link https://source.android.com/docs/automotive/virtualization/reference_platform vsock is used for audio control hal, dumpstate HAL, vehicle HAL. Regards, Peng. > > > > > For a good Xen design, I think the virtio-vsock backend would need > > > to be in Xen itself (the hypervisor). > > > > > > Of course that is more work and it doesn't help you with the > > > specific question you had below :-) > > > > > > For that, I don't have a pointer to help you but maybe others in CC have. > > > > > > Cheers, > > > > > > Stefano > > > > > > > > > On Fri, 23 Feb 2024, Peng Fan wrote: > > > > Hi All, > > > > > > > > Has anyone make virtio-vsock on xen work? My dm args as below: > > > > > > > > virtio = [ > > > > > > > 'backend=0,type=virtio,device,transport=pci,bdf=05:00.0,backend_type > > > =qem > > > u,grant_usage=true' > > > > ] > > > > device_model_args = [ > > > > '-D', '/home/root/qemu_log.txt', > > > > '-d', > > > > 'trace:*vsock*,trace:*vhost*,trace:*virtio*,trace:*pci_update*,tra > > > > ce:* pci_route*,trace:*handle_ioreq*,trace:*xen*', > > > > '-device', > > > > 'vhost-vsock-pci,iommu_platform=false,id=vhost-vsock-pci0,bus=pcie > > > > .0,a > > > > ddr=5.0,guest-cid=3'] > > > > > > > > During my test, it always return failure in dom0 kernel in below code: > > > > > > > > vhost_transport_do_send_pkt { > > > > ... > > > > nbytes = copy_to_iter(hdr, sizeof(*hdr), &iov_iter); > > > > if (nbytes != sizeof(*hdr)) { > > > > vq_err(vq, "Faulted on copying pkt hdr %x > > > > %x %x %px\n", > > > nbytes, sizeof(*hdr), > > > > __builtin_object_size(hdr, 0), &iov_iter); > > > > kfree_skb(skb); > > > > break; > > > > } > > > > } > > > > > > > > I checked copy_to_iter, it is copy data to __user addr, but it > > > > never pass, the copy to __user addr always return 0 bytes copied. > > > > > > > > The asm code "sttr x7, [x6]" will trigger data abort, the kernel > > > > will run into do_page_fault, but lock_mm_and_find_vma report it is > > > > VM_FAULT_BADMAP, that means the __user addr is not mapped, no > vma > > > has this addr. > > > > > > > > I am not sure what may cause this. Appreciate if any comments. > > > > > > > > BTW: I tested blk pci, it works, so the virtio pci should work on my > > > > setup. > > > > > > > > Thanks, > > > > Peng. > > > > > >
