linux-kernel - Re: [PATCH 0/3][RFC] virtio-blk: add io_uring passthrough support for virtio-blk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACGkMEtPdhrXnTYgF4eCC7x7fbh53hgOJ9TytYmZR=z+nFexTQ@mail.gmail.com>
Date: Tue, 17 Dec 2024 10:12:28 +0800
From: Jason Wang <jasowang@...hat.com>
To: Stefan Hajnoczi <stefanha@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>, 
	Ferry Meng <mengferry@...ux.alibaba.com>, "Michael S . Tsirkin" <mst@...hat.com>, 
	linux-block@...r.kernel.org, virtualization@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, io-uring@...r.kernel.org, 
	Joseph Qi <joseph.qi@...ux.alibaba.com>, Jeffle Xu <jefflexu@...ux.alibaba.com>
Subject: Re: [PATCH 0/3][RFC] virtio-blk: add io_uring passthrough support for virtio-blk

On Tue, Dec 17, 2024 at 12:14 AM Stefan Hajnoczi <stefanha@...il.com> wrote:
>
> On Mon, 16 Dec 2024 at 10:54, Christoph Hellwig <hch@...radead.org> wrote:
> >
> > Hacking passthrough into virtio_blk seems like not very good layering.
> > If you have a use case where you want to use the core kernel virtio code
> > but not the protocol drivers we'll probably need a virtqueue passthrough
> > option of some kind.
>
> I think people are finding that submitting I/O via uring_cmd is faster
> than traditional io_uring. The use case isn't really passthrough, it's
> bypass :).
>
> That's why I asked Jens to weigh in on whether there is a generic
> block layer solution here. If uring_cmd is faster then maybe a generic
> uring_cmd I/O interface can be defined without tying applications to
> device-specific commands. Or maybe the traditional io_uring code path
> can be optimized so that bypass is no longer attractive.
>
> The virtio-level virtqueue passthrough idea is interesting for use
> cases that mix passthrough applications with non-passthrough
> applications. VFIO isn't enough because it prevents sharing and
> excludes non-passthrough applications. Something similar to  VDPA
> might be able to pass through just a subset of virtqueues that
> userspace could access via the vhost_vdpa driver.

I thought it could be reused as a mixing approach like this. The vDPA
driver might just do a shadow virtqueue so in fact we just replace
io_uring here with the virtqueue. Or if we think vDPA is heavyweight,
vhost-blk could be another way.

> This approach
> doesn't scale if many applications are running at the same time
> because the number of virtqueues is finite and often the same as the
> number of CPUs.
>
> Stefan
>

Thanks