RE: [PATCH v5 7/8] hisi_acc_vfio_pci: Add support for VFIO live migration

[Shameerali Kolothum Thodi]

> -----Original Message-----
> From: Jason Gunthorpe [mailto:jgg@xxxxxxxxxx]
> Sent: 23 February 2022 00:53
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> linux-crypto@xxxxxxxxxxxxxxx; alex.williamson@xxxxxxxxxx;
> cohuck@xxxxxxxxxx; mgurtovoy@xxxxxxxxxx; yishaih@xxxxxxxxxx; Linuxarm
> <linuxarm@xxxxxxxxxx>; liulongfang <liulongfang@xxxxxxxxxx>; Zengtao (B)
> <prime.zeng@xxxxxxxxxxxxx>; Jonathan Cameron
> <jonathan.cameron@xxxxxxxxxx>; Wangzhou (B) <wangzhou1@xxxxxxxxxxxxx>
> Subject: Re: [PATCH v5 7/8] hisi_acc_vfio_pci: Add support for VFIO live
> migration
> 
> On Mon, Feb 21, 2022 at 11:40:42AM +0000, Shameer Kolothum wrote:
> 
> > +	/*
> > +	 * ACC VF dev BAR2 region consists of both functional register space
> > +	 * and migration control register space. For migration to work, we
> > +	 * need access to both. Hence, we map the entire BAR2 region here.
> > +	 * But from a security point of view, we restrict access to the
> > +	 * migration control space from Guest(Please see mmap/ioctl/read/write
> > +	 * override functions).
> > +	 *
> > +	 * Also the HiSilicon ACC VF devices supported by this driver on
> > +	 * HiSilicon hardware platforms are integrated end point devices
> > +	 * and has no capability to perform PCIe P2P.
> 
> If that is the case why not implement the RUNNING_P2P as well as a
> NOP?
> 
> Alex expressed concerned about proliferation of non-P2P devices as it
> complicates qemu to support mixes

Since both PRE_COPY and P2P are optional, Qemu anyway will have to check and
add the support, right?. Just worried the FSM will look complicated with both
PRE_COPY and P2P arcs now.

Thanks,
Shameer