On 10/11/2023 4:00 PM, Parav Pandit via Virtualization wrote:
Hi Christoph,
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Sent: Wednesday, October 11, 2023 12:29 PM
On Wed, Oct 11, 2023 at 02:43:37AM -0400, Michael S. Tsirkin wrote:
Btw, what is that intel thing everyone is talking about? And why
would the virtio core support vendor specific behavior like that?
It's not a thing it's Zhu Lingshan :) intel is just one of the vendors
that implemented vdpa support and so Zhu Lingshan from intel is
working on vdpa and has also proposed virtio spec extensions for migration.
intel's driver is called ifcvf. vdpa composes all this stuff that is
added to vfio in userspace, so it's a different approach.
Well, so let's call it virtio live migration instead of intel.
And please work all together in the virtio committee that you have one way of
communication between controlling and controlled functions.
If one extension does it one way and the other a different way that's just
creating a giant mess.
We in virtio committee are working on VF device migration where:
VF = controlled function
PF = controlling function
The second proposal is what Michael mentioned from Intel that somehow combine controlled and controlling function as single entity on VF.
The main reasons I find it weird are:
1. it must always need to do mediation to do fake the device reset, and flr flows
2. dma cannot work as you explained for complex device state
3. it needs constant knowledge of each tiny things for each virtio device type
Such single entity appears a bit very weird to me but maybe it is just me.
sorry for the late reply, we have discussed this for weeks in virtio
mailing list.
I have proposed a live migration solution which is a config space solution.
We(me, Jason and Eugenio) have been working on this solution for more
than two years
and we are implementing virtio live migration basic facilities.
The implementation is transport specific, e.g., for PCI we implement new
or extend registers which
work as other config space registers do.
The reason we are arguing is:
I am not sure admin vq based live migration solution is a good choice,
because:
1) it does not work for nested
2) it does not work for bare metal
3) QOS problem
4) security leaks.
Sorry to span the discussions here.
Thanks,
Zhu Lingshan
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