Re: [RFC v2 0/4] vfio/hisilicon: add acc live migration driver

[Jason Gunthorpe]

On Wed, Feb 02, 2022 at 04:10:06PM +0000, Shameerali Kolothum Thodi wrote:
> 
> 
> > From: Jason Gunthorpe [mailto:jgg@xxxxxxxxxx]
> > Sent: 02 February 2022 15:40
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>
> > Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > linux-crypto@xxxxxxxxxxxxxxx; alex.williamson@xxxxxxxxxx;
> > mgurtovoy@xxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx>; liulongfang
> > <liulongfang@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>;
> > yuzenghui <yuzenghui@xxxxxxxxxx>; Jonathan Cameron
> > <jonathan.cameron@xxxxxxxxxx>; Wangzhou (B) <wangzhou1@xxxxxxxxxxxxx>
> > Subject: Re: [RFC v2 0/4] vfio/hisilicon: add acc live migration driver
> > 
> > On Wed, Feb 02, 2022 at 02:34:52PM +0000, Shameerali Kolothum Thodi
> > wrote:
> > 
> > > > There are few topics to consider:
> > > >  - Which of the three feature sets (STOP_COPY, P2P and PRECOPY) make
> > > >    sense for this driver?
> > >
> > > I think it will be STOP_COPY only for now. We might have PRECOPY
> > > feature once we have the SMMUv3 HTTU support in future.
> > 
> > HTTU is the dirty tracking feature? To be clear VFIO migration support for
> > PRECOPY has nothing to do with IOMMU based dirty page tracking.
> 
> Yes, it is based on the IOMMU hardware dirty bit management support.
> A RFC was posted sometime back,
> https://lore.kernel.org/kvm/20210507103608.39440-1-zhukeqian1@xxxxxxxxxx/

Yes, I saw that. I was hoping to have a discussion on this soon about
how to integrate that with the iommufd work, which I hope will allow
that series, and the other IOMMU drivers that can support this to be
merged..

Jason