netdev - Re: [PATCH v4 00/12] remove msize limit in virtio transport

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Date:   Fri, 08 Jul 2022 13:18:40 +0200
From:   Christian Schoenebeck <linux_oss@...debyte.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>,
        Eric Van Hensbergen <ericvh@...il.com>
Cc:     Greg Kurz <groug@...d.org>, Latchesar Ionkov <lucho@...kov.net>,
        Nikolay Kichukov <nikolay@...um.net>, netdev@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net
Subject: Re: [PATCH v4 00/12] remove msize limit in virtio transport

On Freitag, 8. Juli 2022 04:26:40 CEST Eric Van Hensbergen wrote:
> kvmtool might be the easiest I guess - I’m traveling right now but I can
> try and find some others.  The arm fast models have free versions that are
> downloadable as well.  I know I’ve seem some other less-traditional uses of
> virtio particularly in libos deployments but will take some time to rattle
> those from my memory.

Some examples would indeed be useful, thanks!

> On Fri, Jul 8, 2022 at 11:16 AM Dominique Martinet <asmadeus@...ewreck.org>
> 
> wrote:
> > Eric Van Hensbergen wrote on Fri, Jul 08, 2022 at 10:44:45AM +1000:
> > > there are other 9p virtio servers - several emulation platforms support
> > 
> > it
> > 
> > > sans qemu.
> > 
> > Would you happen to have any concrete example?
> > I'd be curious if there are some that'd be easy to setup for test for
> > example; my current validation setup lacks a bit of diversity...
> > 
> > I found https://github.com/moby/hyperkit for OSX but that doesn't really
> > help me, and can't see much else relevant in a quick search

So that appears to be a 9p (@virtio-PCI) client for xhyve, with max. 256kB 
buffers <=> max. 68 virtio descriptors (memory segments) [1]:

/* XXX issues with larger buffers elsewhere in stack */
#define BUFSIZE (1 << 18)
#define MAXDESC (BUFSIZE / 4096 + 4)
#define VT9P_RINGSZ (BUFSIZE / 4096 * 4)

[1] https://github.com/moby/hyperkit/blob/master/src/lib/pci_virtio_9p.c#L27

But on xhyve side I don't see any 9p server implementation:
https://github.com/machyve/xhyve/search?q=9p
Maybe a 9p server is already implemented by Apple's Hypervisor framework. I 
don't find this documented anywhere though.

Best regards,
Christian Schoenebeck