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authorPetr Tesarik <petr.tesarik.ext@huawei.com>2023-08-01 08:24:01 +0200
committerChristoph Hellwig <hch@lst.de>2023-08-01 18:02:20 +0200
commit79636caad3618e2b38457f6e298c9b31ba82b489 (patch)
tree640e81b2730ca902b7be047f0939f562cc3f0125 /include/linux/dma-mapping.h
parent62708b2ba4055cad43a95754e939566b56dde5b6 (diff)
swiotlb: if swiotlb is full, fall back to a transient memory pool
Try to allocate a transient memory pool if no suitable slots can be found and the respective SWIOTLB is allowed to grow. The transient pool is just enough big for this one bounce buffer. It is inserted into a per-device list of transient memory pools, and it is freed again when the bounce buffer is unmapped. Transient memory pools are kept in an RCU list. A memory barrier is required after adding a new entry, because any address within a transient buffer must be immediately recognized as belonging to the SWIOTLB, even if it is passed to another CPU. Deletion does not require any synchronization beyond RCU ordering guarantees. After a buffer is unmapped, its physical addresses may no longer be passed to the DMA API, so the memory range of the corresponding stale entry in the RCU list never matches. If the memory range gets allocated again, then it happens only after a RCU quiescent state. Since bounce buffers can now be allocated from different pools, add a parameter to swiotlb_alloc_pool() to let the caller know which memory pool is used. Add swiotlb_find_pool() to find the memory pool corresponding to an address. This function is now also used by is_swiotlb_buffer(), because a simple boundary check is no longer sufficient. The logic in swiotlb_alloc_tlb() is taken from __dma_direct_alloc_pages(), simplified and enhanced to use coherent memory pools if needed. Note that this is not the most efficient way to provide a bounce buffer, but when a DMA buffer can't be mapped, something may (and will) actually break. At that point it is better to make an allocation, even if it may be an expensive operation. Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'include/linux/dma-mapping.h')
-rw-r--r--include/linux/dma-mapping.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index e13050eb9777..f0ccca16a0ac 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -418,6 +418,8 @@ static inline void dma_sync_sgtable_for_device(struct device *dev,
#define dma_get_sgtable(d, t, v, h, s) dma_get_sgtable_attrs(d, t, v, h, s, 0)
#define dma_mmap_coherent(d, v, c, h, s) dma_mmap_attrs(d, v, c, h, s, 0)
+bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size);
+
static inline void *dma_alloc_coherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp)
{