[RFC PATCH v2 4/6] vfio/spapr: Always clear TCEs before unsetting the window

Shivaprasad G Bhat
2024-04-30T20:11:58Z

The PAPR expects the TCE table to have no entries at the time of
unset window(i.e. remove-pe). The TCE clear right now is done
before freeing the iommu table. On pSeries, the unset window
makes those entries inaccessible to the OS and the H_PUT/GET calls
fail on them with H_CONSTRAINED.

On PowerNV, this has no side effect as the TCE clear can be done
before the DMA window removal as well.

Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
---
drivers/vfio/vfio_iommu_spapr_tce.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index a94ec6225d31..5f9e7e477078 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -364,7 +364,6 @@ static void tce_iommu_release(void *iommu_data)
if (!tbl)
continue;

- tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
tce_iommu_free_table(container, tbl);
}

@@ -720,6 +719,8 @@ static long tce_iommu_remove_window(struct tce_container *container,

BUG_ON(!tbl->it_size);

+ tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
+
/* Detach groups from IOMMUs */
list_for_each_entry(tcegrp, &container->group_list, next) {
table_group = iommu_group_get_iommudata(tcegrp->grp);
@@ -738,7 +739,6 @@ static long tce_iommu_remove_window(struct tce_container *container,
}

/* Free table */
- tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
tce_iommu_free_table(container, tbl);
container->tables[num] = NULL;

@@ -1197,9 +1197,14 @@ static void tce_iommu_release_ownership(struct tce_container *container,
return;
}

- for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i)
- if (container->tables[i])
+ for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
+ if (container->tables[i]) {
+ tce_iommu_clear(container, container->tables[i],
+ container->tables[i]->it_offset,
+ container->tables[i]->it_size);
table_group->ops->unset_window(table_group, i);
+ }
+ }
}

static long tce_iommu_take_ownership(struct tce_container *container,