linux-kernel - [PATCH v5 5/6] iommu/amd: Modify clear_dte

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Message-ID: <20241007041353.4756-6-suravee.suthikulpanit@amd.com>
Date: Mon, 7 Oct 2024 04:13:52 +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>,
	<jgg@...dia.com>, <kevin.tian@...el.com>, <jon.grimm@....com>,
	<santosh.shukla@....com>, <pandoh@...gle.com>, <kumaranand@...gle.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v5 5/6] iommu/amd: Modify clear_dte_entry() to avoid in-place update

Lock DTE and copy value to a temporary storage before update using
cmpxchg128.

Also, refactor the function to simplify logic for applying erratum 63.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/iommu.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 87a7c9dd86d9..dd7b02b00be6 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2106,19 +2106,13 @@ 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)
 {
-	struct dev_table_entry *dev_table = get_dev_table(iommu);
-
-	/* remove entry from the device table seen by the hardware */
-	dev_table[devid].data[0]  = DTE_FLAG_V;
-
-	if (!amd_iommu_snp_en)
-		dev_table[devid].data[0] |= DTE_FLAG_TV;
-
-	dev_table[devid].data[1] &= DTE_FLAG_MASK;
+	struct dev_table_entry new = {};
+	struct dev_table_entry *dte = &get_dev_table(iommu)[dev_data->devid];
 
-	amd_iommu_apply_erratum_63(iommu, devid);
+	make_clear_dte(iommu, dte, &new);
+	update_dte256(iommu, dev_data, &new);
 }
 
 /* Update and flush DTE for the given device */
@@ -2129,7 +2123,7 @@ static void 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