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SubjectRe: [PATCH RFC 02/11] iommu: Add iommu_domain type for SVA
On Sun, Mar 20, 2022 at 02:40:21PM +0800, Lu Baolu wrote:
> Add a new iommu domain type IOMMU_DOMAIN_SVA to represent an I/O page
> table which is shared from CPU host VA. Add a sva_cookie field in the
> iommu_domain structure to save the mm_struct which represent the CPU
> memory page table.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> include/linux/iommu.h | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 36f43af0af53..3e179b853380 100644
> +++ b/include/linux/iommu.h
> @@ -64,6 +64,9 @@ struct iommu_domain_geometry {
> #define __IOMMU_DOMAIN_PT (1U << 2) /* Domain is identity mapped */
> #define __IOMMU_DOMAIN_DMA_FQ (1U << 3) /* DMA-API uses flush queue */
>
> +#define __IOMMU_DOMAIN_SHARED (1U << 4) /* Page table shared from CPU */
> +#define __IOMMU_DOMAIN_HOST_VA (1U << 5) /* Host CPU virtual address */
> +
> /*
> * This are the possible domain-types
> *
> @@ -86,6 +89,8 @@ struct iommu_domain_geometry {
> #define IOMMU_DOMAIN_DMA_FQ (__IOMMU_DOMAIN_PAGING | \
> __IOMMU_DOMAIN_DMA_API | \
> __IOMMU_DOMAIN_DMA_FQ)
> +#define IOMMU_DOMAIN_SVA (__IOMMU_DOMAIN_SHARED | \
> + __IOMMU_DOMAIN_HOST_VA)

Is there any use for this in the core code? I feel like flags should
only be created if the core code needs to test them in some way.

> @@ -95,6 +100,7 @@ struct iommu_domain {
> void *handler_token;
> struct iommu_domain_geometry geometry;
> struct iommu_dma_cookie *iova_cookie;
> + struct mm_struct *sva_cookie;

Don't call a mm_struct a cookie please

And why do we need this in core code?

Jason

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