Re: device compatibility interface for live migration with assigned devices
On Fri, Aug 28, 2020 at 03:04:12PM +0100, Sean Mooney wrote:
On Fri, 2020-08-28 at 15:47 +0200, Cornelia Huck wrote:
> On Wed, 26 Aug 2020 14:41:17 +0800
> Yan Zhao <yan.y.zhao(a)intel.com> wrote:
>
> > previously, we want to regard the two mdevs created with dsa-1dwq x 30 and
> > dsa-2dwq x 15 as compatible, because the two mdevs consist equal resources.
> >
> > But, as it's a burden to upper layer, we agree that if this condition
> > happens, we still treat the two as incompatible.
> >
> > To fix it, either the driver should expose dsa-1dwq only, or the target
> > dsa-2dwq needs to be destroyed and reallocated via dsa-1dwq x 30.
>
> AFAIU, these are mdev types, aren't they? So, basically, any management
> software needs to take care to use the matching mdev type on the target
> system for device creation?
or just do the simple thing of use the same mdev type on the source and dest.
matching mdevtypes is not nessiarly trivial. we could do that but we woudl have
to do that in python rather then sql so it would be slower to do at least today.
we dont currently have the ablity to say the resouce provider must have 1 of these
set of traits. just that we must have a specific trait. this is a feature we have
disucssed a couple of times and delayed untill we really really need it but its not out
of the question that we could add it for this usecase. i suspect however we would do
exact
match first and explore this later after the inital mdev migration works.
Yes, I think it's good.
still, I'd like to put it more explicitly to make ensure it's not missed:
the reason we want to specify compatible_type as a trait and check
whether target compatible_type is the superset of source
compatible_type is for the consideration of backward compatibility.
e.g.
an old generation device may have a mdev type xxx-v4-yyy, while a newer
generation device may be of mdev type xxx-v5-yyy.
with the compatible_type traits, the old generation device is still
able to be regarded as compatible to newer generation device even their
mdev types are not equal.
Thanks
Yan
by the way i was looking at some vdpa reslated matiail today and
noticed vdpa devices are nolonger
usign mdevs and and now use a vhost chardev so i guess we will need a completely seperate
mechanioum
for vdpa vs mdev migration as a result. that is rather unfortunet but i guess that is
life.
>