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

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Message-ID: <20240829180726.5022-3-suravee.suthikulpanit@amd.com>
Date: Thu, 29 Aug 2024 18:07:23 +0000
From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To: <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>
CC: <joro@...tes.org>, <robin.murphy@....com>, <vasant.hegde@....com>,
	<ubizjak@...il.com>, <jgg@...dia.com>, <jon.grimm@....com>,
	<santosh.shukla@....com>, <pandoh@...gle.com>, <kumaranand@...gle.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 2/5] iommu/amd: Introduce rw_semaphore for Device Table Entry (DTE)

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@....com>
---
 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