[PATCH v1 04/10] powerpc/kernel/iommu: Add new iommu_table_in_use() helper

Leonardo Bras
2020-08-17T23:41:16Z

Having a function to check if the iommu table has any allocation helps
deciding if a tbl can be reset for using a new DMA window.

It should be enough to replace all instances of !bitmap_empty(tbl...).

iommu_table_in_use() skips reserved memory, so we don't need to worry about
releasing it before testing. This causes iommu_table_release_pages() to
become unnecessary, given it is only used to remove reserved memory for
testing.

Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
---
arch/powerpc/include/asm/iommu.h | 1 +
arch/powerpc/kernel/iommu.c | 62 ++++++++++++++++++--------------
2 files changed, 37 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index 5032f1593299..2913e5c8b1f8 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -154,6 +154,7 @@ extern int iommu_tce_table_put(struct iommu_table *tbl);
*/
extern struct iommu_table *iommu_init_table(struct iommu_table *tbl,
int nid, unsigned long res_start, unsigned long res_end);
+bool iommu_table_in_use(struct iommu_table *tbl);

#define IOMMU_TABLE_GROUP_MAX_TABLES 2

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 7f603d4e62d4..c5d5d36ab65e 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -668,21 +668,6 @@ static void iommu_table_reserve_pages(struct iommu_table *tbl,
set_bit(i - tbl->it_offset, tbl->it_map);
}

-static void iommu_table_release_pages(struct iommu_table *tbl)
-{
- int i;
-
- /*
- * In case we have reserved the first bit, we should not emit
- * the warning below.
- */
- if (tbl->it_offset == 0)
- clear_bit(0, tbl->it_map);
-
- for (i = tbl->it_reserved_start; i < tbl->it_reserved_end; ++i)
- clear_bit(i - tbl->it_offset, tbl->it_map);
-}
-
/*
* Build a iommu_table structure. This contains a bit map which
* is used to manage allocation of the tce space.
@@ -743,6 +728,38 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid,
return tbl;
}

+bool iommu_table_in_use(struct iommu_table *tbl)
+{
+ bool in_use;
+ unsigned long p1_start = 0, p1_end, p2_start, p2_end;
+
+ /*ignore reserved bit0*/
+ if (tbl->it_offset == 0)
+ p1_start = 1;
+
+ /* Check if reserved memory is valid*/
+ if (tbl->it_reserved_start >= tbl->it_offset &&
+ tbl->it_reserved_start <= (tbl->it_offset + tbl->it_size) &&
+ tbl->it_reserved_end >= tbl->it_offset &&
+ tbl->it_reserved_end <= (tbl->it_offset + tbl->it_size)) {
+ p1_end = tbl->it_reserved_start - tbl->it_offset;
+ p2_start = tbl->it_reserved_end - tbl->it_offset + 1;
+ p2_end = tbl->it_size;
+ } else {
+ p1_end = tbl->it_size;
+ p2_start = 0;
+ p2_end = 0;
+ }
+
+ in_use = (find_next_bit(tbl->it_map, p1_end, p1_start) != p1_end);
+ if (in_use || p2_start == 0)
+ return in_use;
+
+ in_use = (find_next_bit(tbl->it_map, p2_end, p2_start) != p2_end);
+
+ return in_use;
+}
+
static void iommu_table_free(struct kref *kref)
{
unsigned long bitmap_sz;
@@ -759,10 +776,8 @@ static void iommu_table_free(struct kref *kref)
return;
}

- iommu_table_release_pages(tbl);
-
/* verify that table contains no entries */
- if (!bitmap_empty(tbl->it_map, tbl->it_size))
+ if (iommu_table_in_use(tbl))
pr_warn("%s: Unexpected TCEs\n", __func__);

/* calculate bitmap size in bytes */
@@ -1069,18 +1084,13 @@ int iommu_take_ownership(struct iommu_table *tbl)
for (i = 0; i < tbl->nr_pools; i++)
spin_lock(&tbl->pools[i].lock);

- iommu_table_release_pages(tbl);
-
- if (!bitmap_empty(tbl->it_map, tbl->it_size)) {
+ if (iommu_table_in_use(tbl)) {
pr_err("iommu_tce: it_map is not empty");
ret = -EBUSY;
- /* Undo iommu_table_release_pages, i.e. restore bit#0, etc */
- iommu_table_reserve_pages(tbl, tbl->it_reserved_start,
- tbl->it_reserved_end);
- } else {
- memset(tbl->it_map, 0xff, sz);
}

+ memset(tbl->it_map, 0xff, sz);
+
for (i = 0; i < tbl->nr_pools; i++)
spin_unlock(&tbl->pools[i].lock);
spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
--
2.25.4