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SubjectRe: [PATCH v1] iommu/s390: Declare s390 iommu reserved regions
On 17/01/2019 10:23, Shameerali Kolothum Thodi wrote:
> Hi Pierre,
>> -----Original Message-----
>> From: Pierre Morel []
>> Sent: 15 January 2019 17:37
>> To:
>> Cc:;;
>>; Shameerali Kolothum Thodi
>> <>;
>> 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]
>> 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
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

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


Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany

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