Re: [PATCH v12 2/8] iommu: Move global PASID allocation from SVA to core

[Jason Gunthorpe]

On Wed, Aug 02, 2023 at 02:24:21PM -0700, Jacob Pan wrote:
> Intel ENQCMD requires a single PASID to be shared between multiple
> devices, as the PASID is stored in a single MSR register per-process
> and userspace can use only that one PASID.
> 
> This means that the PASID allocation for any ENQCMD using device driver
> must always come from a shared global pool, regardless of what kind of
> domain the PASID will be used with.
> 
> Split the code for the global PASID allocator into
> iommu_alloc/free_global_pasid() so that drivers can attach non-SVA
> domains to PASIDs as well.
> 
> This patch moves global PASID allocation APIs from SVA to IOMMU APIs.
> Reserved PASIDs, currently only RID_PASID, are excluded from the global
> PASID allocation.
> 
> It is expected that device drivers will use the allocated PASIDs to
> attach to appropriate IOMMU domains for use.
> 
> Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
> v8: fix off-by-one in max_pasid check
> v7: simplify range check (Baolu)
> v6: explicitly exclude reserved a range from SVA PASID allocation
>     check mm PASID compatibility with device
> v5: move PASID range check inside API so that device drivers only pass
>     in struct device* (Kevin)
> v4: move dummy functions outside ifdef CONFIG_IOMMU_SVA (Baolu)
> ---
>  drivers/iommu/iommu-sva.c | 29 ++++++++++-------------------
>  drivers/iommu/iommu.c     | 28 ++++++++++++++++++++++++++++
>  include/linux/iommu.h     | 10 ++++++++++
>  3 files changed, 48 insertions(+), 19 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason