[PATCH 4/5] iommu: Support mm PASID 1:n with sva domains

Tina Zhang
2023-08-08T16:44:06Z

Each mm bound to devices gets a PASID and corresponding sva domains
allocated in iommu_sva_bind_device(), which are referenced by iommu_mm
field of the mm. The PASID is released in __mmdrop(), while a sva domain
is released when on one is using it (the reference count is decremented
in iommu_sva_unbind_device()).

Since the required info of PASID and sva domains is kept in struct
iommu_mm_data of a mm, use mm->iommu_mm field instead of the old pasid
field in mm struct. The sva domain list is protected by iommu_sva_lock.

Besides, this patch removes mm_pasid_init(), as with the introduced
iommu_mm structure, initializing mm pasid in mm_init() is unnecessary.

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
---
drivers/iommu/iommu-sva.c | 38 +++++++++++++++++++++++++-------------
include/linux/iommu.h | 10 +++-------
kernel/fork.c | 1 -
3 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 0a4a1ed40814..35366f51ad27 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -15,6 +15,7 @@ static DEFINE_IDA(iommu_global_pasid_ida);
/* Allocate a PASID for the mm within range (inclusive) */
static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
{
+ struct iommu_mm_data *iommu_mm = NULL;
int ret = 0;

if (min == IOMMU_PASID_INVALID ||
@@ -33,11 +34,22 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
goto out;
}

+ iommu_mm = kzalloc(sizeof(struct iommu_mm_data), GFP_KERNEL);
+ if (!iommu_mm) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
- if (ret < 0)
+ if (ret < 0) {
+ kfree(iommu_mm);
goto out;
+ }
+
+ iommu_mm->pasid = ret;
+ mm->iommu_mm = iommu_mm;
+ INIT_LIST_HEAD(&mm->iommu_mm->sva_domains);

- mm->pasid = ret;
ret = 0;
out:
mutex_unlock(&iommu_sva_lock);
@@ -82,16 +94,12 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm

mutex_lock(&iommu_sva_lock);
/* Search for an existing domain. */
- domain = iommu_get_domain_for_dev_pasid(dev, mm_get_pasid(mm),
- IOMMU_DOMAIN_SVA);
- if (IS_ERR(domain)) {
- ret = PTR_ERR(domain);
- goto out_unlock;
- }
-
- if (domain) {
- domain->users++;
- goto out;
+ list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next) {
+ ret = iommu_attach_device_pasid(domain, dev, mm_get_pasid(mm));
+ if (!ret) {
+ domain->users++;
+ goto out;
+ }
}

/* Allocate a new domain and set it on device pasid. */
@@ -105,6 +113,8 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
if (ret)
goto out_free_domain;
domain->users = 1;
+ list_add(&domain->next, &mm->iommu_mm->sva_domains);
+
out:
mutex_unlock(&iommu_sva_lock);
handle->dev = dev;
@@ -137,8 +147,9 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
struct device *dev = handle->dev;

mutex_lock(&iommu_sva_lock);
+ iommu_detach_device_pasid(domain, dev, pasid);
if (--domain->users == 0) {
- iommu_detach_device_pasid(domain, dev, pasid);
+ list_del(&domain->next);
iommu_domain_free(domain);
}
mutex_unlock(&iommu_sva_lock);
@@ -218,4 +229,5 @@ void mm_pasid_drop(struct mm_struct *mm)
return;

ida_free(&iommu_global_pasid_ida, mm_get_pasid(mm));
+ kfree(mm->iommu_mm);
}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 435d1c1afd23..6a87df6d8637 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -109,6 +109,7 @@ struct iommu_domain {
struct { /* IOMMU_DOMAIN_SVA */
struct mm_struct *mm;
int users;
+ struct list_head next;
};
};
};
@@ -1177,17 +1178,13 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
}

#ifdef CONFIG_IOMMU_SVA
-static inline void mm_pasid_init(struct mm_struct *mm)
-{
- mm->pasid = IOMMU_PASID_INVALID;
-}
static inline bool mm_valid_pasid(struct mm_struct *mm)
{
- return mm->pasid != IOMMU_PASID_INVALID;
+ return mm->iommu_mm ? true : false;
}
static inline u32 mm_get_pasid(struct mm_struct *mm)
{
- return mm->pasid;
+ return mm->iommu_mm ? mm->iommu_mm->pasid : IOMMU_PASID_INVALID;
}
void mm_pasid_drop(struct mm_struct *mm);
struct iommu_sva *iommu_sva_bind_device(struct device *dev,
@@ -1209,7 +1206,6 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
{
return IOMMU_PASID_INVALID;
}
-static inline void mm_pasid_init(struct mm_struct *mm) {}
static inline bool mm_valid_pasid(struct mm_struct *mm) { return false; }
static inline u32 mm_get_pasid(struct mm_struct *mm)
{
diff --git a/kernel/fork.c b/kernel/fork.c
index d2e12b6d2b18..f06392dd1ca8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1274,7 +1274,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm_init_cpumask(mm);
mm_init_aio(mm);
mm_init_owner(mm, p);
- mm_pasid_init(mm);
RCU_INIT_POINTER(mm->exe_file, NULL);
mmu_notifier_subscriptions_init(mm);
init_tlb_flush_pending(mm);
--
2.17.1