From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Roman Kiryanov <rkir@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
virtio-dev@lists.oasis-open.org, Lingfeng Yang <lfy@google.com>
Subject: Re: [virtio-dev] Memory sharing device
Date: Tue, 5 Feb 2019 10:04:27 +0000 [thread overview]
Message-ID: <20190205100427.GA2693@work-vm> (raw)
In-Reply-To: <CAOGAQeq3psE=FxnU9+T1G79Y8_9mb3H8LKXWXnzY5-kGcX6RBA@mail.gmail.com>
* Roman Kiryanov (rkir@google.com) wrote:
> Hi Gerd,
>
> > virtio-gpu specifically needs that to support vulkan and opengl
> > extensions for coherent buffers, which must be allocated by the host gpu
> > driver. It's WIP still.
>
Hi Roman,
> the proposed spec says:
>
> +Shared memory regions MUST NOT be used to control the operation
> +of the device, nor to stream data; those should still be performed
> +using virtqueues.
Yes, I put that in.
> Is there a strong reason to prohibit using memory regions for control purposes?
> Our long term goal is to have as few kernel drivers as possible and to move
> "drivers" into userspace. If we go with the virtqueues, is there
> general a purpose
> device/driver to talk between our host and guest to support custom hardware
> (with own blobs)? Could you please advise if we can use something else to
> achieve this goal?
My reason for that paragraph was to try and think about what should
still be in the virtqueues; after all a device that *just* shares a
block of memory and does everything in the block of memory itself isn't
really a virtio device - it's the standardised queue structure that
makes it a virtio device.
However, I'd be happy to accept the 'MUST NOT' might be a bit strong for
some cases where there's stuff that makes sense in the queues and
stuff that makes sense differently.
> I saw there were registers added, could you please elaborate how new address
> regions are added and associated with the host memory (and backwards)?
In virtio-fs we have two separate stages:
a) A shared arena is setup (and that's what the spec Stefan pointed to is about) -
it's statically allocated at device creation and corresponds to a chunk
of guest physical address space
b) During operation the guest kernel asks for files to be mapped into
part of that arena dynamically, using commands sent over the queue
- our queue carries FUSE commands, and we've added two new FUSE
commands to perform the map/unmap. They talk in terms of offsets
within the shared arena, rather than GPAs.
So I'd tried to start by doing the spec for (a).
> We allocate a region from the guest first and pass its offset to the
> host to plug
> real RAM into it and then we mmap this offset:
>
> https://photos.app.goo.gl/NJvPBvvFS3S3n9mn6
How do you transmit the glMapBufferRange command from QEMU driver to
host?
Dave
> Thank you.
>
> Regards,
> Roman.
>
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--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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next prev parent reply other threads:[~2019-02-05 10:04 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-01 20:34 [virtio-dev] Memory sharing device Roman Kiryanov
2019-02-04 5:40 ` Stefan Hajnoczi
2019-02-04 10:13 ` Gerd Hoffmann
2019-02-04 10:18 ` Roman Kiryanov
2019-02-05 7:42 ` Roman Kiryanov
2019-02-05 10:04 ` Dr. David Alan Gilbert [this message]
2019-02-05 15:17 ` Frank Yang
2019-02-05 15:21 ` Frank Yang
2019-02-05 21:06 ` Roman Kiryanov
2019-02-06 7:03 ` Gerd Hoffmann
2019-02-06 15:09 ` Frank Yang
2019-02-06 15:11 ` Frank Yang
2019-02-08 7:57 ` Stefan Hajnoczi
2019-02-08 14:46 ` Frank Yang
2019-02-06 20:14 ` Dr. David Alan Gilbert
2019-02-06 20:27 ` Frank Yang
2019-02-07 12:10 ` Cornelia Huck
2019-02-11 14:49 ` Michael S. Tsirkin
2019-02-11 15:14 ` Frank Yang
2019-02-11 15:25 ` Frank Yang
2019-02-12 13:01 ` Michael S. Tsirkin
2019-02-12 13:16 ` Dr. David Alan Gilbert
2019-02-12 13:27 ` Michael S. Tsirkin
2019-02-12 16:17 ` Frank Yang
2019-02-19 7:17 ` Gerd Hoffmann
2019-02-19 15:59 ` Frank Yang
2019-02-20 6:51 ` Gerd Hoffmann
2019-02-20 15:31 ` Frank Yang
2019-02-21 6:55 ` Gerd Hoffmann
2019-02-19 7:12 ` Gerd Hoffmann
2019-02-19 16:02 ` Frank Yang
2019-02-20 7:02 ` Gerd Hoffmann
2019-02-20 15:32 ` Frank Yang
2019-02-21 7:29 ` Gerd Hoffmann
2019-02-21 9:24 ` Dr. David Alan Gilbert
2019-02-21 9:59 ` Gerd Hoffmann
2019-02-21 10:03 ` Dr. David Alan Gilbert
2019-02-22 6:15 ` Michael S. Tsirkin
2019-02-22 6:42 ` Gerd Hoffmann
2019-02-11 16:57 ` Michael S. Tsirkin
2019-02-12 8:27 ` Roman Kiryanov
2019-02-12 11:25 ` Dr. David Alan Gilbert
2019-02-12 13:47 ` Cornelia Huck
2019-02-12 14:03 ` Michael S. Tsirkin
2019-02-12 15:56 ` Frank Yang
2019-02-12 16:46 ` Dr. David Alan Gilbert
2019-02-12 17:20 ` Frank Yang
2019-02-12 17:26 ` Frank Yang
2019-02-12 19:06 ` Michael S. Tsirkin
2019-02-13 2:50 ` Frank Yang
2019-02-13 4:02 ` Michael S. Tsirkin
2019-02-13 4:19 ` Michael S. Tsirkin
2019-02-13 4:59 ` Frank Yang
2019-02-13 18:18 ` Frank Yang
2019-02-14 7:15 ` Frank Yang
2019-02-22 22:05 ` Michael S. Tsirkin
2019-02-24 21:19 ` Frank Yang
2019-02-13 4:59 ` Frank Yang
2019-02-19 7:54 ` Gerd Hoffmann
2019-02-19 15:54 ` Frank Yang
2019-02-20 3:46 ` Michael S. Tsirkin
2019-02-20 15:24 ` Frank Yang
2019-02-20 19:29 ` Michael S. Tsirkin
2019-02-20 6:25 ` Gerd Hoffmann
2019-02-20 15:30 ` Frank Yang
2019-02-20 15:35 ` Frank Yang
2019-02-21 6:44 ` Gerd Hoffmann
2019-02-12 18:22 ` Michael S. Tsirkin
2019-02-12 19:01 ` Frank Yang
2019-02-12 19:15 ` Michael S. Tsirkin
2019-02-12 20:15 ` Frank Yang
2019-02-12 13:00 ` Michael S. Tsirkin
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