[PATCH v2 2/5] iommu/amd: Introduce rw_semaphore for Device Table Entry (DTE)

From: Suravee Suthikulpanit
Date: Thu Aug 29 2024 - 14:08:38 EST


In preparation for 256-bit DTE update, each DTE access/update needs
to be protected using synchronication mechanism to prevent conflict.

Introduce a new rw-semaphore struct dev_data.dte_sem, which is per
device. Also update certain helper functions to use the new dte_sem.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
drivers/iommu/amd/amd_iommu_types.h | 1 +
drivers/iommu/amd/iommu.c | 10 ++++++++--
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index c9f9a598eb82..65f3a073999d 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -833,6 +833,7 @@ struct devid_map {
struct iommu_dev_data {
/*Protect against attach/detach races */
spinlock_t lock;
+ struct rw_semaphore dte_sem;

struct list_head list; /* For domain->dev_list */
struct llist_node dev_data_list; /* For global dev_data_list */
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 87c5385ce3f2..994ed02842b9 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -205,6 +205,7 @@ static struct iommu_dev_data *alloc_dev_data(struct amd_iommu *iommu, u16 devid)
return NULL;

spin_lock_init(&dev_data->lock);
+ init_rwsem(&dev_data->dte_sem);
dev_data->devid = devid;
ratelimit_default_init(&dev_data->rs);

@@ -1946,10 +1947,13 @@ static void set_dte_entry(struct amd_iommu *iommu,
}
}

-static void clear_dte_entry(struct amd_iommu *iommu, u16 devid)
+static void clear_dte_entry(struct amd_iommu *iommu, struct iommu_dev_data *dev_data)
{
+ u16 devid = dev_data->devid;
struct dev_table_entry *dev_table = get_dev_table(iommu);

+ down_write(&dev_data->dte_sem);
+
/* remove entry from the device table seen by the hardware */
dev_table[devid].data[0] = DTE_FLAG_V;

@@ -1959,6 +1963,8 @@ static void clear_dte_entry(struct amd_iommu *iommu, u16 devid)
dev_table[devid].data[1] &= DTE_FLAG_MASK;

amd_iommu_apply_erratum_63(iommu, devid);
+
+ up_write(&dev_data->dte_sem);
}

/* Update and flush DTE for the given device */
@@ -1969,7 +1975,7 @@ void amd_iommu_dev_update_dte(struct iommu_dev_data *dev_data, bool set)
if (set)
set_dte_entry(iommu, dev_data);
else
- clear_dte_entry(iommu, dev_data->devid);
+ clear_dte_entry(iommu, dev_data);

clone_aliases(iommu, dev_data->dev);
device_flush_dte(dev_data);
--
2.34.1