Re: [PATCH v2 12/16] iommu/amd: Add support for different types of PPR handler

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, Jul 28, 2023 at 05:36:05AM +0000, Vasant Hegde wrote:
> From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> 
> For AMD IOMMU, the PPR feature is needed to support IO page fault (IOPF).
> PPR is enabled per PCI end-point device, and is configured by the PPR bit
> in the IOMMU device table entry (i.e DTE[PPR]).
> 
> Currently, PPR is enabled for a device when it is initialized for AMD
> IOMMU v2API. To support paging for IOPF, the DTE[PPR] bit needs to be
> updated when enable/disable IOPF feature.
> 
> Introducing struct iommu_dev_data.ppr and enum ppr_handlers to track PPR
> setting for each device.
> 
> Finally iommu_dev_data.ppr is set only when IOMMU supports PPR. Hence
> remove redundant feature support check in set_dte_entry().
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> Co-developed-by: Vasant Hegde <vasant.hegde@amd.com>
> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
> ---
>  drivers/iommu/amd/amd_iommu_types.h |  7 +++++++
>  drivers/iommu/amd/iommu.c           | 10 ++++------
>  drivers/iommu/amd/iommu_v2.c        | 14 +++++++++++++-
>  3 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
> index a066f375ba87..321d361dfb60 100644
> --- a/drivers/iommu/amd/amd_iommu_types.h
> +++ b/drivers/iommu/amd/amd_iommu_types.h
> @@ -803,6 +803,12 @@ struct devid_map {
>  	bool cmd_line;
>  };
>  
> +enum ppr_handlers {
> +	PPR_HANDLER_NONE,	/* No handler specified */
> +	PPR_HANDLER_V2API,	/* IOMMU v2 API ppr handler */
> +	PPR_HANDLER_IOPF,	/* IOPF ppr handler */

This constant is never used, move it to the patch that uses it.

Why are you doing this? It would be much better to hook the GPU driver
into the standard API, what prevents that?

Jason