Re: [PATCH v1] iommu/s390: Declare s390 iommu reserved regions

[Pierre Morel]

On 17/01/2019 10:23, Shameerali Kolothum Thodi wrote:
> Hi Pierre,
>
> > -----Original Message-----
> > From: Pierre Morel [mailto:pmorel@xxxxxxxxxxxxx]
> > Sent: 15 January 2019 17:37
> > To: gerald.schaefer@xxxxxxxxxx
> > Cc: joro@xxxxxxxxxx; linux-s390@xxxxxxxxxxxxxxx;
> > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > alex.williamson@xxxxxxxxxx; Shameerali Kolothum Thodi
> > <shameerali.kolothum.thodi@xxxxxxxxxx>; walling@xxxxxxxxxxxxx
> > Subject: [PATCH v1] iommu/s390: Declare s390 iommu reserved regions
> >
> > The s390 iommu can only allow DMA transactions between the zPCI device
> > entries start_dma and end_dma.
> >
> > Let's declare the regions before start_dma and after end_dma as
> > reserved regions using the appropriate callback in iommu_ops.
> >
> > The reserved region may later be retrieved from sysfs or from
> > the vfio iommu internal interface.
>
> Just in case you are planning to use the sysfs interface to retrieve the valid
> regions, and intend to use that in Qemu vfio path, please see the discussion
> here [1] (If you haven't seen this already)
>
> Thanks,
> Shameer
>
> [1] https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg03651.html
>   
> > This seems to me related with the work Shameer has started on
> > vfio_iommu_type1 so I add Alex and Shameer to the CC list.
> >
> > Pierre Morel (1):
> >    iommu/s390: Declare s390 iommu reserved regions
> >
> >   drivers/iommu/s390-iommu.c | 29 +++++++++++++++++++++++++++++
> >   1 file changed, 29 insertions(+)
> >
> > --
> > 2.7.4

Thanks Shameer,

Interesting discussion indeed.

AFAIK the patch series you are working on will provide a way to retrieve 
the reserved region through the VFIO IOMMU interface, using capabilities 
in the VFIO_IOMMU_GET_INFO.
Before this patch, the iommu_type1 was not able to retrieve the 
forbidden region from the s390_iommu.

See this patch is a contribution, so that these regions will appear in 
the reserved list when the VFIO_IOMM_GET_INFO will be able to report the 
information.

I am expecting to be able to to retrieve this information from the 
VFIO_IOMMU_GET_INFO syscall as soon as it is available.

Regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany