[PATCH v5 5/6] iommu/amd: Modify clear_dte_entry() to avoid in-place update

From: Suravee Suthikulpanit
Date: Mon Oct 07 2024 - 00:16:11 EST


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@xxxxxxx>
---
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