linux-kernel - [RFC v2 06/11] nvme-pci: add support for dmabuf reggistration

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Message-ID: <9bc25f46d2116436d73140cd8e8554576de2caca.1763725388.git.asml.silence@gmail.com>
Date: Sun, 23 Nov 2025 22:51:26 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: linux-block@...r.kernel.org,
	io-uring@...r.kernel.org
Cc: Vishal Verma <vishal1.verma@...el.com>,
	tushar.gohad@...el.com,
	Keith Busch <kbusch@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Pavel Begunkov <asml.silence@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-nvme@...ts.infradead.org,
	linux-fsdevel@...r.kernel.org,
	linux-media@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org
Subject: [RFC v2 06/11] nvme-pci: add support for dmabuf reggistration

Implement dma-token related callbacks for nvme block devices.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 drivers/nvme/host/pci.c | 95 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index e5ca8301bb8b..63e03c3dc044 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -27,6 +27,7 @@
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/sed-opal.h>
+#include <linux/blk-mq-dma-token.h>
 
 #include "trace.h"
 #include "nvme.h"
@@ -482,6 +483,92 @@ static void nvme_release_descriptor_pools(struct nvme_dev *dev)
 	}
 }
 
+static void nvme_dmabuf_move_notify(struct dma_buf_attachment *attach)
+{
+	blk_mq_dma_map_move_notify(attach->importer_priv);
+}
+
+const struct dma_buf_attach_ops nvme_dmabuf_importer_ops = {
+	.move_notify = nvme_dmabuf_move_notify,
+	.allow_peer2peer = true,
+};
+
+static int nvme_init_dma_token(struct request_queue *q,
+				struct blk_mq_dma_token *token)
+{
+	struct dma_buf_attachment *attach;
+	struct nvme_ns *ns = q->queuedata;
+	struct nvme_dev *dev = to_nvme_dev(ns->ctrl);
+	struct dma_buf *dmabuf = token->dmabuf;
+
+	if (dmabuf->size % NVME_CTRL_PAGE_SIZE)
+		return -EINVAL;
+
+	attach = dma_buf_dynamic_attach(dmabuf, dev->dev,
+					&nvme_dmabuf_importer_ops, token);
+	if (IS_ERR(attach))
+		return PTR_ERR(attach);
+
+	token->private = attach;
+	return 0;
+}
+
+static void nvme_clean_dma_token(struct request_queue *q,
+				 struct blk_mq_dma_token *token)
+{
+	struct dma_buf_attachment *attach = token->private;
+
+	dma_buf_detach(token->dmabuf, attach);
+}
+
+static int nvme_dma_map(struct request_queue *q, struct blk_mq_dma_map *map)
+{
+	struct blk_mq_dma_token *token = map->token;
+	struct dma_buf_attachment *attach = token->private;
+	unsigned nr_entries;
+	unsigned long tmp, i = 0;
+	struct scatterlist *sg;
+	struct sg_table *sgt;
+	dma_addr_t *dma_list;
+
+	nr_entries = token->dmabuf->size / NVME_CTRL_PAGE_SIZE;
+	dma_list = kmalloc_array(nr_entries, sizeof(dma_list[0]), GFP_KERNEL);
+	if (!dma_list)
+		return -ENOMEM;
+
+	sgt = dma_buf_map_attachment(attach, token->dir);
+	if (IS_ERR(sgt)) {
+		kfree(dma_list);
+		return PTR_ERR(sgt);
+	}
+	map->sgt = sgt;
+
+	for_each_sgtable_dma_sg(sgt, sg, tmp) {
+		dma_addr_t dma = sg_dma_address(sg);
+		unsigned long sg_len = sg_dma_len(sg);
+
+		while (sg_len) {
+			dma_list[i++] = dma;
+			dma += NVME_CTRL_PAGE_SIZE;
+			sg_len -= NVME_CTRL_PAGE_SIZE;
+		}
+	}
+
+	map->private = dma_list;
+	return 0;
+}
+
+static void nvme_dma_unmap(struct request_queue *q, struct blk_mq_dma_map *map)
+{
+	struct blk_mq_dma_token *token = map->token;
+	struct dma_buf_attachment *attach = token->private;
+	dma_addr_t *dma_list = map->private;
+
+	dma_buf_unmap_attachment_unlocked(attach, map->sgt, token->dir);
+	map->sgt = NULL;
+	kfree(dma_list);
+}
+
 static int nvme_init_hctx_common(struct blk_mq_hw_ctx *hctx, void *data,
 		unsigned qid)
 {
@@ -1067,6 +1154,9 @@ static blk_status_t nvme_map_data(struct request *req)
 	struct blk_dma_iter iter;
 	blk_status_t ret;
 
+	if (req->bio && bio_flagged(req->bio, BIO_DMA_TOKEN))
+		return BLK_STS_RESOURCE;
+
 	/*
 	 * Try to skip the DMA iterator for single segment requests, as that
 	 * significantly improves performances for small I/O sizes.
@@ -2093,6 +2183,11 @@ static const struct blk_mq_ops nvme_mq_ops = {
 	.map_queues	= nvme_pci_map_queues,
 	.timeout	= nvme_timeout,
 	.poll		= nvme_poll,
+
+	.dma_map	= nvme_dma_map,
+	.dma_unmap 	= nvme_dma_unmap,
+	.init_dma_token =  nvme_init_dma_token,
+	.clean_dma_token = nvme_clean_dma_token,
 };
 
 static void nvme_dev_remove_admin(struct nvme_dev *dev)
-- 
2.52.0