[v2,3/4] dma-pool: Introduce dma_guess_pool()
diff mbox series

Message ID 20200714123928.8581-4-nsaenzjulienne@suse.de
State Accepted
Commit 48b6703858dd5526c82d8ff2dbac59acab3a9dda
Headers show
  • dma-pool: Fix atomic pool selection
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Commit Message

Nicolas Saenz Julienne July 14, 2020, 12:39 p.m. UTC
dma-pool's dev_to_pool() creates the false impression that there is a
way to grantee a mapping between a device's DMA constraints and an
atomic pool. It tuns out it's just a guess, and the device might need to
use an atomic pool containing memory from a 'safer' (or lower) memory

To help mitigate this, introduce dma_guess_pool() which can be fed a
device's DMA constraints and atomic pools already known to be faulty, in
order for it to provide an better guess on which pool to use.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
 kernel/dma/pool.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff mbox series

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 318035e093fb..5b9eaa2b498d 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -203,7 +203,7 @@  static int __init dma_atomic_pool_init(void)
-static inline struct gen_pool *dev_to_pool(struct device *dev)
+static inline struct gen_pool *dma_guess_pool_from_device(struct device *dev)
 	u64 phys_mask;
 	gfp_t gfp;
@@ -217,10 +217,30 @@  static inline struct gen_pool *dev_to_pool(struct device *dev)
 	return atomic_pool_kernel;
+static inline struct gen_pool *dma_get_safer_pool(struct gen_pool *bad_pool)
+	if (bad_pool == atomic_pool_kernel)
+		return atomic_pool_dma32 ? : atomic_pool_dma;
+	if (bad_pool == atomic_pool_dma32)
+		return atomic_pool_dma;
+	return NULL;
+static inline struct gen_pool *dma_guess_pool(struct device *dev,
+					      struct gen_pool *bad_pool)
+	if (bad_pool)
+		return dma_get_safer_pool(bad_pool);
+	return dma_guess_pool_from_device(dev);
 void *dma_alloc_from_pool(struct device *dev, size_t size,
 			  struct page **ret_page, gfp_t flags)
-	struct gen_pool *pool = dev_to_pool(dev);
+	struct gen_pool *pool = dma_guess_pool(dev, NULL);
 	unsigned long val;
 	void *ptr = NULL;
@@ -249,7 +269,7 @@  void *dma_alloc_from_pool(struct device *dev, size_t size,
 bool dma_free_from_pool(struct device *dev, void *start, size_t size)
-	struct gen_pool *pool = dev_to_pool(dev);
+	struct gen_pool *pool = dma_guess_pool(dev, NULL);
 	if (!pool || !gen_pool_has_addr(pool, (unsigned long)start, size))
 		return false;