Re: [PATCH v5 04/12] iommu/sva: Basic data structures for SVA

Jean-Philippe Brucker
2022-05-03T18:09:56Z

On Mon, May 02, 2022 at 09:48:34AM +0800, Lu Baolu wrote:
> Use below data structures for SVA implementation in the IOMMU core:
>
> - struct iommu_sva_ioas
> Represent the I/O address space shared with an application CPU address
> space. This structure has a 1:1 relationship with an mm_struct. It
> grabs a "mm->mm_count" refcount during creation and drop it on release.

Do we actually need this structure? At the moment it only keeps track of
bonds, which we can move to struct dev_iommu. Replacing it by a mm pointer
in struct iommu_domain simplifies the driver and seems to work

Thanks,
Jean

>
> - struct iommu_domain (IOMMU_DOMAIN_SVA type)
> Represent a hardware pagetable that the IOMMU hardware could use for
> SVA translation. Multiple iommu domains could be bound with an SVA ioas
> and each grabs a refcount from ioas in order to make sure ioas could
> only be freed after all domains have been unbound.
>
> - struct iommu_sva
> Represent a bond relationship between an SVA ioas and an iommu domain.
> If a bond already exists, it's reused and a reference is taken.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> include/linux/iommu.h | 14 +++++++++++++-
> drivers/iommu/iommu-sva-lib.h | 1 +
> drivers/iommu/iommu-sva-lib.c | 18 ++++++++++++++++++
> 3 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index ab36244d4e94..f582f434c513 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -42,6 +42,7 @@ struct notifier_block;
> struct iommu_sva;
> struct iommu_fault_event;
> struct iommu_dma_cookie;
> +struct iommu_sva_ioas;
>
> /* iommu fault flags */
> #define IOMMU_FAULT_READ 0x0
> @@ -64,6 +65,9 @@ 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 +90,8 @@ 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)
>
> struct iommu_domain {
> unsigned type;
> @@ -95,6 +101,7 @@ struct iommu_domain {
> void *handler_token;
> struct iommu_domain_geometry geometry;
> struct iommu_dma_cookie *iova_cookie;
> + struct iommu_sva_ioas *sva_ioas;
> };
>
> static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
> @@ -628,7 +635,12 @@ struct iommu_fwspec {
> * struct iommu_sva - handle to a device-mm bond
> */
> struct iommu_sva {
> - struct device *dev;
> + struct device *dev;
> + struct iommu_sva_ioas *sva_ioas;
> + struct iommu_domain *domain;
> + /* Link to sva ioas's bonds list */
> + struct list_head node;
> + refcount_t users;
> };
>
> int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
> diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
> index 8909ea1094e3..9c5e108e2c8a 100644
> --- a/drivers/iommu/iommu-sva-lib.h
> +++ b/drivers/iommu/iommu-sva-lib.h
> @@ -10,6 +10,7 @@
>
> int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
> struct mm_struct *iommu_sva_find(ioasid_t pasid);
> +struct mm_struct *iommu_sva_domain_mm(struct iommu_domain *domain);
>
> /* I/O Page fault */
> struct device;
> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> index 106506143896..d524a402be3b 100644
> --- a/drivers/iommu/iommu-sva-lib.c
> +++ b/drivers/iommu/iommu-sva-lib.c
> @@ -3,6 +3,8 @@
> * Helpers for IOMMU drivers implementing SVA
> */
> #include <linux/mutex.h>
> +#include <linux/iommu.h>
> +#include <linux/slab.h>
> #include <linux/sched/mm.h>
>
> #include "iommu-sva-lib.h"
> @@ -10,6 +12,22 @@
> static DEFINE_MUTEX(iommu_sva_lock);
> static DECLARE_IOASID_SET(iommu_sva_pasid);
>
> +struct iommu_sva_ioas {
> + struct mm_struct *mm;
> + ioasid_t pasid;
> +
> + /* Counter of domains attached to this ioas. */
> + refcount_t users;
> +
> + /* All bindings are linked here. */
> + struct list_head bonds;
> +};
> +
> +struct mm_struct *iommu_sva_domain_mm(struct iommu_domain *domain)
> +{
> + return domain->sva_ioas->mm;
> +}
> +
> /**
> * iommu_sva_alloc_pasid - Allocate a PASID for the mm
> * @mm: the mm
> --
> 2.25.1
>