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Subject[PATCH 0/5 v4] Fix virtio-blk issue with SWIOTLB
Date

Hi,

here is the fourth version of this patch-set. Previous
versions can be found here:

V1: https://lore.kernel.org/lkml/20190110134433.15672-1-joro@8bytes.org/

V2: https://lore.kernel.org/lkml/20190115132257.6426-1-joro@8bytes.org/

V3: https://lore.kernel.org/lkml/20190123163049.24863-1-joro@8bytes.org/

The problem solved here is a limitation of the SWIOTLB implementation,
which does not support allocations larger than 256kb. When the
virtio-blk driver tries to read/write a block larger than that, the
allocation of the dma-handle fails and an IO error is reported.

For all changes to v3, a diff to v3 of the patch-set is at
the end of this email.

Please review.

Thanks,

Joerg

Joerg Roedel (5):
swiotlb: Introduce swiotlb_max_mapping_size()
swiotlb: Add is_swiotlb_active() function
dma: Introduce dma_max_mapping_size()
virtio: Introduce virtio_max_dma_size()
virtio-blk: Consider virtio_max_dma_size() for maximum segment size

Documentation/DMA-API.txt | 8 ++++++++
drivers/block/virtio_blk.c | 10 ++++++----
drivers/virtio/virtio_ring.c | 10 ++++++++++
include/linux/dma-mapping.h | 16 ++++++++++++++++
include/linux/swiotlb.h | 11 +++++++++++
include/linux/virtio.h | 2 ++
kernel/dma/direct.c | 11 +++++++++++
kernel/dma/swiotlb.c | 14 ++++++++++++++
8 files changed, 78 insertions(+), 4 deletions(-)

--
2.17.1

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index e133ccd60228..acfe3d0f78d1 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -195,6 +195,14 @@ Requesting the required mask does not alter the current mask. If you
wish to take advantage of it, you should issue a dma_set_mask()
call to set the mask to the value returned.

+::
+
+ size_t
+ dma_direct_max_mapping_size(struct device *dev);
+
+Returns the maximum size of a mapping for the device. The size parameter
+of the mapping functions like dma_map_single(), dma_map_page() and
+others should not be larger than the returned value.

Part Id - Streaming DMA mappings
--------------------------------
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 5c087d330b4b..e9e786b4b598 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -62,7 +62,7 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,

extern int
swiotlb_dma_supported(struct device *hwdev, u64 mask);
-extern size_t swiotlb_max_mapping_size(struct device *dev);
+size_t swiotlb_max_mapping_size(struct device *dev);
bool is_swiotlb_active(void);

#ifdef CONFIG_SWIOTLB
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 9fbd075081d9..c873f9cc2146 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -670,5 +670,9 @@ size_t swiotlb_max_mapping_size(struct device *dev)

bool is_swiotlb_active(void)
{
- return !no_iotlb_memory;
+ /*
+ * When SWIOTLB is initialized, even if io_tlb_start points to physical
+ * address zero, io_tlb_end surely doesn't.
+ */
+ return io_tlb_end != 0;
}
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