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@xxxxxxxxx> 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. > > >
