[PATCHv3 0/2] blk-mq-dma: p2p cleanups and integrity fixup

[PATCHv3 0/2] blk-mq-dma: p2p cleanups and integrity fixup

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

This series moves the p2p dma tracking from the caller to the block
layer, and makes it possible to actually use p2p for metadata payloads.

v2 had a mistake when CONFIG_BLK_DEV_INTEGRITY was not enabled, and this
update fixes that.

Keith Busch (2):
  blk-integrity: enable p2p source and destination
  blk-mq-dma: bring back p2p request flags

 block/bio-integrity.c         | 21 +++++++++++++++++----
 block/blk-mq-dma.c            |  4 ++++
 drivers/nvme/host/pci.c       | 21 ++++-----------------
 include/linux/bio-integrity.h |  1 +
 include/linux/blk-integrity.h | 15 +++++++++++++++
 include/linux/blk-mq-dma.h    | 11 +++++++++--
 include/linux/blk_types.h     |  2 ++
 7 files changed, 52 insertions(+), 23 deletions(-)

-- 
2.47.3

[PATCHv3 1/2] blk-integrity: enable p2p source and destination

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

Set the extraction flags to allow p2p pages for the metadata buffer if
the block device allows it. Similar to data payloads, ensure the bio
does not use merging if we see a p2p page.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/bio-integrity.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 6b077ca937f6b..d3618ed106f4e 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -230,7 +230,8 @@ static int bio_integrity_init_user(struct bio *bio, struct bio_vec *bvec,
 }
 
 static unsigned int bvec_from_pages(struct bio_vec *bvec, struct page **pages,
-				    int nr_vecs, ssize_t bytes, ssize_t offset)
+				    int nr_vecs, ssize_t bytes, ssize_t offset,
+				    bool *is_p2p)
 {
 	unsigned int nr_bvecs = 0;
 	int i, j;
@@ -251,6 +252,9 @@ static unsigned int bvec_from_pages(struct bio_vec *bvec, struct page **pages,
 			bytes -= next;
 		}
 
+		if (is_pci_p2pdma_page(pages[i]))
+			*is_p2p = true;
+
 		bvec_set_page(&bvec[nr_bvecs], pages[i], size, offset);
 		offset = 0;
 		nr_bvecs++;
@@ -265,10 +269,11 @@ int bio_integrity_map_user(struct bio *bio, struct iov_iter *iter)
 	unsigned int align = blk_lim_dma_alignment_and_pad(&q->limits);
 	struct page *stack_pages[UIO_FASTIOV], **pages = stack_pages;
 	struct bio_vec stack_vec[UIO_FASTIOV], *bvec = stack_vec;
+	iov_iter_extraction_t extraction_flags = 0;
 	size_t offset, bytes = iter->count;
+	bool copy, is_p2p = false;
 	unsigned int nr_bvecs;
 	int ret, nr_vecs;
-	bool copy;
 
 	if (bio_integrity(bio))
 		return -EINVAL;
@@ -286,15 +291,23 @@ int bio_integrity_map_user(struct bio *bio, struct iov_iter *iter)
 	}
 
 	copy = !iov_iter_is_aligned(iter, align, align);
-	ret = iov_iter_extract_pages(iter, &pages, bytes, nr_vecs, 0, &offset);
+
+	if (blk_queue_pci_p2pdma(q))
+		extraction_flags |= ITER_ALLOW_P2PDMA;
+
+	ret = iov_iter_extract_pages(iter, &pages, bytes, nr_vecs,
+					extraction_flags, &offset);
 	if (unlikely(ret < 0))
 		goto free_bvec;
 
-	nr_bvecs = bvec_from_pages(bvec, pages, nr_vecs, bytes, offset);
+	nr_bvecs = bvec_from_pages(bvec, pages, nr_vecs, bytes, offset,
+				   &is_p2p);
 	if (pages != stack_pages)
 		kvfree(pages);
 	if (nr_bvecs > queue_max_integrity_segments(q))
 		copy = true;
+	if (is_p2p)
+		bio->bi_opf |= REQ_NOMERGE;
 
 	if (copy)
 		ret = bio_integrity_copy_user(bio, bvec, nr_bvecs, bytes);
-- 
2.47.3

[PATCHv3 2/2] blk-mq-dma: bring back p2p request flags

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

We only need to consider data and metadata dma mapping types separately.
The request and bio integrity payload have enough flag bits to
internally track the mapping type for each. Use these so the caller
doesn't need to track them, and provide separete request and integrity
helpers to the common code. This will make it easier to scale new
mappings, like the proposed MMIO attribute, without burdening the caller
to track such things.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/blk-mq-dma.c            |  4 ++++
 drivers/nvme/host/pci.c       | 21 ++++-----------------
 include/linux/bio-integrity.h |  1 +
 include/linux/blk-integrity.h | 15 +++++++++++++++
 include/linux/blk-mq-dma.h    | 11 +++++++++--
 include/linux/blk_types.h     |  2 ++
 6 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index 660b5e200ccf6..449950029872a 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -174,6 +174,10 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,
 	switch (pci_p2pdma_state(&iter->p2pdma, dma_dev,
 				 phys_to_page(vec.paddr))) {
 	case PCI_P2PDMA_MAP_BUS_ADDR:
+		if (iter->iter.is_integrity)
+			bio_integrity(req->bio)->bip_flags |= BIP_P2P_DMA;
+		else
+			req->cmd_flags |= REQ_P2PDMA;
 		return blk_dma_map_bus(iter, &vec);
 	case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
 		/*
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index d8a9dee55de33..28e203b894eb1 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -260,12 +260,6 @@ enum nvme_iod_flags {
 	/* single segment dma mapping */
 	IOD_SINGLE_SEGMENT	= 1U << 2,
 
-	/* DMA mapped with PCI_P2PDMA_MAP_BUS_ADDR */
-	IOD_P2P_BUS_ADDR	= 1U << 3,
-
-	/* Metadata DMA mapped with PCI_P2PDMA_MAP_BUS_ADDR */
-	IOD_META_P2P_BUS_ADDR	= 1U << 4,
-
 	/* Metadata using non-coalesced MPTR */
 	IOD_SINGLE_META_SEGMENT	= 1U << 5,
 };
@@ -737,9 +731,8 @@ static void nvme_unmap_metadata(struct request *req)
 		return;
 	}
 
-	if (!blk_rq_dma_unmap(req, dma_dev, &iod->meta_dma_state,
-				iod->meta_total_len,
-				iod->flags & IOD_META_P2P_BUS_ADDR)) {
+	if (!blk_rq_integrity_dma_unmap(req, dma_dev, &iod->meta_dma_state,
+					iod->meta_total_len)) {
 		if (nvme_pci_cmd_use_meta_sgl(&iod->cmd))
 			nvme_free_sgls(req, sge, &sge[1]);
 		else
@@ -766,8 +759,7 @@ static void nvme_unmap_data(struct request *req)
 		return;
 	}
 
-	if (!blk_rq_dma_unmap(req, dma_dev, &iod->dma_state, iod->total_len,
-				iod->flags & IOD_P2P_BUS_ADDR)) {
+	if (!blk_rq_dma_unmap(req, dma_dev, &iod->dma_state, iod->total_len)) {
 		if (nvme_pci_cmd_use_sgl(&iod->cmd))
 			nvme_free_sgls(req, iod->descriptors[0],
 				       &iod->cmd.common.dptr.sgl);
@@ -1043,9 +1035,6 @@ static blk_status_t nvme_map_data(struct request *req)
 	if (!blk_rq_dma_map_iter_start(req, dev->dev, &iod->dma_state, &iter))
 		return iter.status;
 
-	if (iter.p2pdma.map == PCI_P2PDMA_MAP_BUS_ADDR)
-		iod->flags |= IOD_P2P_BUS_ADDR;
-
 	if (use_sgl == SGL_FORCED ||
 	    (use_sgl == SGL_SUPPORTED &&
 	     (sgl_threshold && nvme_pci_avg_seg_size(req) >= sgl_threshold)))
@@ -1068,9 +1057,7 @@ static blk_status_t nvme_pci_setup_meta_sgls(struct request *req)
 						&iod->meta_dma_state, &iter))
 		return iter.status;
 
-	if (iter.p2pdma.map == PCI_P2PDMA_MAP_BUS_ADDR)
-		iod->flags |= IOD_META_P2P_BUS_ADDR;
-	else if (blk_rq_dma_map_coalesce(&iod->meta_dma_state))
+	if (blk_rq_dma_map_coalesce(&iod->meta_dma_state))
 		entries = 1;
 
 	/*
diff --git a/include/linux/bio-integrity.h b/include/linux/bio-integrity.h
index 0a25716820fe0..851254f36eb36 100644
--- a/include/linux/bio-integrity.h
+++ b/include/linux/bio-integrity.h
@@ -13,6 +13,7 @@ enum bip_flags {
 	BIP_CHECK_GUARD		= 1 << 5, /* guard check */
 	BIP_CHECK_REFTAG	= 1 << 6, /* reftag check */
 	BIP_CHECK_APPTAG	= 1 << 7, /* apptag check */
+	BIP_P2P_DMA		= 1 << 8, /* using P2P address */
 };
 
 struct bio_integrity_payload {
diff --git a/include/linux/blk-integrity.h b/include/linux/blk-integrity.h
index 78fe2459e6612..b659373788f60 100644
--- a/include/linux/blk-integrity.h
+++ b/include/linux/blk-integrity.h
@@ -27,6 +27,15 @@ static inline bool queue_limits_stack_integrity_bdev(struct queue_limits *t,
 
 #ifdef CONFIG_BLK_DEV_INTEGRITY
 int blk_rq_map_integrity_sg(struct request *, struct scatterlist *);
+
+static inline bool blk_rq_integrity_dma_unmap(struct request *req,
+		struct device *dma_dev, struct dma_iova_state *state,
+		size_t mapped_len)
+{
+	return blk_dma_unmap(req, dma_dev, state, mapped_len,
+			bio_integrity(req->bio)->bip_flags & BIP_P2P_DMA);
+}
+
 int blk_rq_count_integrity_sg(struct request_queue *, struct bio *);
 int blk_rq_integrity_map_user(struct request *rq, void __user *ubuf,
 			      ssize_t bytes);
@@ -115,6 +124,12 @@ static inline int blk_rq_map_integrity_sg(struct request *q,
 {
 	return 0;
 }
+static inline bool blk_rq_integrity_dma_unmap(struct request *req,
+		struct device *dma_dev, struct dma_iova_state *state,
+		size_t mapped_len)
+{
+	return false;
+}
 static inline int blk_rq_integrity_map_user(struct request *rq,
 					    void __user *ubuf,
 					    ssize_t bytes)
diff --git a/include/linux/blk-mq-dma.h b/include/linux/blk-mq-dma.h
index 0f45ea110ca12..51829958d8729 100644
--- a/include/linux/blk-mq-dma.h
+++ b/include/linux/blk-mq-dma.h
@@ -43,7 +43,7 @@ static inline bool blk_rq_dma_map_coalesce(struct dma_iova_state *state)
 }
 
 /**
- * blk_rq_dma_unmap - try to DMA unmap a request
+ * blk_dma_unmap - try to DMA unmap a request
  * @req:	request to unmap
  * @dma_dev:	device to unmap from
  * @state:	DMA IOVA state
@@ -53,7 +53,7 @@ static inline bool blk_rq_dma_map_coalesce(struct dma_iova_state *state)
  * Returns %false if the callers need to manually unmap every DMA segment
  * mapped using @iter or %true if no work is left to be done.
  */
-static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
+static inline bool blk_dma_unmap(struct request *req, struct device *dma_dev,
 		struct dma_iova_state *state, size_t mapped_len, bool is_p2p)
 {
 	if (is_p2p)
@@ -68,4 +68,11 @@ static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
 	return !dma_need_unmap(dma_dev);
 }
 
+static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
+		struct dma_iova_state *state, size_t mapped_len)
+{
+	return blk_dma_unmap(req, dma_dev, state, mapped_len,
+				req->cmd_flags & REQ_P2PDMA);
+}
+
 #endif /* BLK_MQ_DMA_H */
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 930daff207df2..09b99d52fd365 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -386,6 +386,7 @@ enum req_flag_bits {
 	__REQ_DRV,		/* for driver use */
 	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
 	__REQ_ATOMIC,		/* for atomic write operations */
+	__REQ_P2PDMA,		/* contains P2P DMA pages */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -418,6 +419,7 @@ enum req_flag_bits {
 #define REQ_DRV		(__force blk_opf_t)(1ULL << __REQ_DRV)
 #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_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 
-- 
2.47.3

Re: [PATCHv3 0/2] blk-mq-dma: p2p cleanups and integrity fixup

[Jens Axboe]

On Wed, 03 Sep 2025 12:33:15 -0700, Keith Busch wrote:
> This series moves the p2p dma tracking from the caller to the block
> layer, and makes it possible to actually use p2p for metadata payloads.
> 
> v2 had a mistake when CONFIG_BLK_DEV_INTEGRITY was not enabled, and this
> update fixes that.
> 
> Keith Busch (2):
>   blk-integrity: enable p2p source and destination
>   blk-mq-dma: bring back p2p request flags
> 
> [...]

Applied, thanks!

[1/2] blk-integrity: enable p2p source and destination
      commit: 05ceea5d3ec9a1b1d6858ffd4739fdb0ed1b8eaf
[2/2] blk-mq-dma: bring back p2p request flags
      commit: d57447ffb5fadffdba920f2fb933296fb6c5ff57

Best regards,
-- 
Jens Axboe