Re: [PATCH v1 00/22] vfio: Adopt iommufd

[Jason Gunthorpe]

On Mon, Sep 18, 2023 at 02:23:48PM +0200, Cédric Le Goater wrote:
> On 9/18/23 13:51, Jason Gunthorpe wrote:
> > On Fri, Sep 15, 2023 at 02:42:48PM +0200, Cédric Le Goater wrote:
> > > On 8/30/23 12:37, Zhenzhong Duan wrote:
> > > > Hi All,
> > > > 
> > > > As the kernel side iommufd cdev and hot reset feature have been queued,
> > > > also hwpt alloc has been added in Jason's for_next branch [1], I'd like
> > > > to update a new version matching kernel side update and with rfc flag
> > > > removed. Qemu code can be found at [2], look forward more comments!
> > > 
> > > FYI, I have started cleaning up the VFIO support in QEMU PPC. First
> > > is the removal of nvlink2, which was dropped from the kernel 2.5 years
> > > ago. Next is probably removal of all the PPC bits in VFIO. Code is
> > > bitrotting and AFAICT VFIO has been broken on these platforms since
> > > 5.18 or so.
> > 
> > It was fixed since then - at least one company (not IBM) still cares
> > about vfio on ppc, though I think it is for a DPDK use case not VFIO.
> 
> Indeed.
> I just checked on a POWER9 box running a debian sid (6.4) and device
> assignment of a simple NIC (e1000e) in a ubuntu 23.04 guest worked
> correctly. Using a 6.6-rc1 on the host worked also. One improvement
> would be to reflect in the Kconfig files that CONFIG_IOMMUFD is not
> supported on PPC so that it can not be selected.

When we did this I thought there were other iommu drivers on Power
that did work with VFIO (fsl_pamu specifically), but it turns out that
ppc iommu driver doesn't support VFIO and the VFIO FSL stuff is for
ARM only.

So it could be done...

These days I believe we have the capacity to do the PPC stuff without
making it so special - it would be alot of work but the road is pretty
clear. At least if qemu wants to remove PPC VFIO support I would not
object.

Jason