[PATCH v2 15/16] block-dma: properly take MMIO path

[Leon Romanovsky]

From: Leon Romanovsky <leonro at nvidia.com>

Make sure that CPU is not synced and IOMMU is configured to take
MMIO path by providing newly introduced DMA_ATTR_MMIO attribute.

Signed-off-by: Leon Romanovsky <leonro at nvidia.com>
---
 block/blk-mq-dma.c         | 13 +++++++++++--
 include/linux/blk-mq-dma.h |  6 +++++-
 include/linux/blk_types.h  |  2 ++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index 37e2142be4f7..d415088ed9fd 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -87,8 +87,13 @@ static bool blk_dma_map_bus(struct blk_dma_iter *iter, struct phys_vec *vec)
 static bool blk_dma_map_direct(struct request *req, struct device *dma_dev,
 		struct blk_dma_iter *iter, struct phys_vec *vec)
 {
+	unsigned int attrs = 0;
+
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
+
 	iter->addr = dma_map_phys(dma_dev, vec->paddr, vec->len,
-			rq_dma_dir(req), 0);
+			rq_dma_dir(req), attrs);
 	if (dma_mapping_error(dma_dev, iter->addr)) {
 		iter->status = BLK_STS_RESOURCE;
 		return false;
@@ -103,14 +108,17 @@ static bool blk_rq_dma_map_iova(struct request *req, struct device *dma_dev,
 {
 	enum dma_data_direction dir = rq_dma_dir(req);
 	unsigned int mapped = 0;
+	unsigned int attrs = 0;
 	int error;
 
 	iter->addr = state->addr;
 	iter->len = dma_iova_size(state);
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
 
 	do {
 		error = dma_iova_link(dma_dev, state, vec->paddr, mapped,
-				vec->len, dir, 0);
+				vec->len, dir, attrs);
 		if (error)
 			break;
 		mapped += vec->len;
@@ -176,6 +184,7 @@ bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,
 			 * same as non-P2P transfers below and during unmap.
 			 */
 			req->cmd_flags &= ~REQ_P2PDMA;
+			req->cmd_flags |= REQ_MMIO;
 			break;
 		default:
 			iter->status = BLK_STS_INVAL;
diff --git a/include/linux/blk-mq-dma.h b/include/linux/blk-mq-dma.h
index c26a01aeae00..6c55f5e58511 100644
--- a/include/linux/blk-mq-dma.h
+++ b/include/linux/blk-mq-dma.h
@@ -48,12 +48,16 @@ static inline bool blk_rq_dma_map_coalesce(struct dma_iova_state *state)
 static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
 		struct dma_iova_state *state, size_t mapped_len)
 {
+	unsigned int attrs = 0;
+
 	if (req->cmd_flags & REQ_P2PDMA)
 		return true;
 
 	if (dma_use_iova(state)) {
+		if (req->cmd_flags & REQ_MMIO)
+			attrs = DMA_ATTR_MMIO;
 		dma_iova_destroy(dma_dev, state, mapped_len, rq_dma_dir(req),
-				 0);
+				 attrs);
 		return true;
 	}
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 09b99d52fd36..283058bcb5b1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -387,6 +387,7 @@ enum req_flag_bits {
 	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
 	__REQ_ATOMIC,		/* for atomic write operations */
 	__REQ_P2PDMA,		/* contains P2P DMA pages */
+	__REQ_MMIO,		/* contains MMIO memory */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -420,6 +421,7 @@ enum req_flag_bits {
 #define REQ_FS_PRIVATE	(__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
 #define REQ_ATOMIC	(__force blk_opf_t)(1ULL << __REQ_ATOMIC)
 #define REQ_P2PDMA	(__force blk_opf_t)(1ULL << __REQ_P2PDMA)
+#define REQ_MMIO	(__force blk_opf_t)(1ULL << __REQ_MMIO)
 
 #define REQ_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 
-- 
2.50.1