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RE: question about virtio-vsock on xen
- To: Oleksandr Tyshchenko <Oleksandr_Tyshchenko@xxxxxxxx>
- From: Peng Fan <peng.fan@xxxxxxx>
- Date: Tue, 27 Feb 2024 00:40:20 +0000
- Accept-language: en-US
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- Cc: Julien Grall <julien@xxxxxxx>, "vikram.garhwal@xxxxxxx" <vikram.garhwal@xxxxxxx>, Leo Yan <leo.yan@xxxxxxxxxx>, Viresh Kumar <viresh.kumar@xxxxxxxxxx>, Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, "sgarzare@xxxxxxxxxx" <sgarzare@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxx>
- Delivery-date: Tue, 27 Feb 2024 00:40:26 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AdpmUSXKZvg8Aft6RRu9smUwoggtbwAUAHAAACuPlYAARFRfYAAj+0EAAAkpkYA=
- Thread-topic: question about virtio-vsock on xen
> Subject: Re: question about virtio-vsock on xen
>
>
>
> 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.
Thanks for sharing me the information. I need to learn more stuff:)
Thanks,
Peng.
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