sva: Basic data structures for SVA

Baolu Lu Wed, 04 May 2022 23:42:46 -0700

On 2022/5/4 02:09, Jean-Philippe Brucker wrote:

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


Fair enough.

+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;
+};

By moving @mm to struct iommu_domain and @bonds to struct dev_iommu, the
code looks simpler. The mm, sva domain and per-device dev_iommu are
guaranteed to be valid during bind() and unbind().

Will head this direction in the next version.


Thanks,
Jean


Best regards,
baolu


- 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...@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


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

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