[PATCH v3 07/10] nvme-pci: implement dma_token backed requests

[Pavel Begunkov <asml.silence@gmail.com>]

Enable BIO_DMABUF_MAP backed requests. It creates a prp list for the
dmabuf when it's mapped, which is then used to initialise requests.

Suggested-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 drivers/nvme/host/pci.c | 282 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 282 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index db5fc9bf6627..d2629853a972 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -27,6 +27,8 @@
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/sed-opal.h>
+#include <linux/io_dmabuf_token.h>
+#include <linux/dma-resv.h>
 
 #include "trace.h"
 #include "nvme.h"
@@ -393,6 +395,17 @@ struct nvme_queue {
 	struct completion delete_done;
 };
 
+struct nvme_dmabuf_token {
+	struct dma_buf_attachment *attach;
+};
+
+struct nvme_dmabuf_map {
+	struct io_dmabuf_map base;
+	dma_addr_t *dma_list;
+	struct sg_table *sgt;
+	unsigned nr_entries;
+};
+
 /* bits for iod->flags */
 enum nvme_iod_flags {
 	/* this command has been aborted by the timeout handler */
@@ -854,6 +867,134 @@ static void nvme_free_descriptors(struct request *req)
 	}
 }
 
+static void nvme_dmabuf_map_sync(struct nvme_dev *nvme_dev, struct request *req,
+				 bool for_cpu)
+{
+	int length = blk_rq_payload_bytes(req);
+	struct device *dev = nvme_dev->dev;
+	enum dma_data_direction dma_dir;
+	struct bio *bio = req->bio;
+	struct nvme_dmabuf_map *map;
+	dma_addr_t *dma_list;
+	int offset, map_idx;
+
+	dma_dir = rq_data_dir(req) == READ ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+	map = container_of(bio->dmabuf_map, struct nvme_dmabuf_map, base);
+	dma_list = map->dma_list;
+
+	offset = bio->bi_iter.bi_bvec_done;
+	map_idx = offset / NVME_CTRL_PAGE_SIZE;
+	length += offset & (NVME_CTRL_PAGE_SIZE - 1);
+
+	while (length > 0) {
+		u64 dma_addr = dma_list[map_idx++];
+
+		if (for_cpu)
+			__dma_sync_single_for_cpu(dev, dma_addr,
+						  NVME_CTRL_PAGE_SIZE, dma_dir);
+		else
+			__dma_sync_single_for_device(dev, dma_addr,
+						     NVME_CTRL_PAGE_SIZE,
+						     dma_dir);
+		length -= NVME_CTRL_PAGE_SIZE;
+	}
+}
+
+static void nvme_rq_clean_dmabuf_map(struct nvme_dev *dev,
+				      struct request *req)
+{
+	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
+
+	nvme_dmabuf_map_sync(dev, req, true);
+
+	if (!(iod->flags & IOD_SINGLE_SEGMENT))
+		nvme_free_descriptors(req);
+}
+
+static blk_status_t nvme_rq_setup_dmabuf_map(struct request *req,
+					     struct nvme_queue *nvmeq)
+{
+	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
+	int length = blk_rq_payload_bytes(req);
+	u64 dma_addr, prp1_dma, prp2_dma;
+	struct bio *bio = req->bio;
+	struct nvme_dmabuf_map *map;
+	dma_addr_t *dma_list;
+	dma_addr_t prp_dma;
+	__le64 *prp_list;
+	int i, map_idx;
+	int offset;
+
+	nvme_dmabuf_map_sync(nvmeq->dev, req, false);
+
+	map = container_of(bio->dmabuf_map, struct nvme_dmabuf_map, base);
+	dma_list = map->dma_list;
+
+	offset = bio->bi_iter.bi_bvec_done;
+	map_idx = offset / NVME_CTRL_PAGE_SIZE;
+	offset &= (NVME_CTRL_PAGE_SIZE - 1);
+	prp1_dma = dma_list[map_idx++] + offset;
+
+	length -= (NVME_CTRL_PAGE_SIZE - offset);
+	if (length <= 0) {
+		prp2_dma = 0;
+		goto done;
+	}
+
+	if (length <= NVME_CTRL_PAGE_SIZE) {
+		prp2_dma = dma_list[map_idx];
+		goto done;
+	}
+
+	if (DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE) <=
+	    NVME_SMALL_POOL_SIZE / sizeof(__le64))
+		iod->flags |= IOD_SMALL_DESCRIPTOR;
+
+	prp_list = dma_pool_alloc(nvme_dma_pool(nvmeq, iod), GFP_ATOMIC,
+			&prp_dma);
+	if (!prp_list)
+		return BLK_STS_RESOURCE;
+
+	iod->descriptors[iod->nr_descriptors++] = prp_list;
+	prp2_dma = prp_dma;
+	i = 0;
+	for (;;) {
+		if (i == NVME_CTRL_PAGE_SIZE >> 3) {
+			__le64 *old_prp_list = prp_list;
+
+			prp_list = dma_pool_alloc(nvmeq->descriptor_pools.large,
+					GFP_ATOMIC, &prp_dma);
+			if (!prp_list)
+				goto free_prps;
+			iod->descriptors[iod->nr_descriptors++] = prp_list;
+			prp_list[0] = old_prp_list[i - 1];
+			old_prp_list[i - 1] = cpu_to_le64(prp_dma);
+			i = 1;
+		}
+
+		dma_addr = dma_list[map_idx++];
+		prp_list[i++] = cpu_to_le64(dma_addr);
+
+		length -= NVME_CTRL_PAGE_SIZE;
+		if (length <= 0)
+			break;
+	}
+done:
+	iod->cmd.common.dptr.prp1 = cpu_to_le64(prp1_dma);
+	iod->cmd.common.dptr.prp2 = cpu_to_le64(prp2_dma);
+	return BLK_STS_OK;
+free_prps:
+	nvme_free_descriptors(req);
+	return BLK_STS_RESOURCE;
+}
+
+static inline bool nvme_rq_is_dmabuf_attached(struct request *req)
+{
+	if (!IS_ENABLED(CONFIG_DMABUF_TOKEN))
+		return false;
+	return req->bio && bio_flagged(req->bio, BIO_DMABUF_MAP);
+}
+
 static void nvme_free_prps(struct request *req, unsigned int attrs)
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
@@ -932,6 +1073,11 @@ static void nvme_unmap_data(struct request *req)
 	struct device *dma_dev = nvmeq->dev->dev;
 	unsigned int attrs = 0;
 
+	if (nvme_rq_is_dmabuf_attached(req)) {
+		nvme_rq_clean_dmabuf_map(nvmeq->dev, req);
+		return;
+	}
+
 	if (iod->flags & IOD_SINGLE_SEGMENT) {
 		static_assert(offsetof(union nvme_data_ptr, prp1) ==
 				offsetof(union nvme_data_ptr, sgl.addr));
@@ -1222,6 +1368,9 @@ static blk_status_t nvme_map_data(struct request *req)
 	struct blk_dma_iter iter;
 	blk_status_t ret;
 
+	if (nvme_rq_is_dmabuf_attached(req))
+		return nvme_rq_setup_dmabuf_map(req, nvmeq);
+
 	/*
 	 * Try to skip the DMA iterator for single segment requests, as that
 	 * significantly improves performances for small I/O sizes.
@@ -2238,6 +2387,134 @@ static int nvme_create_queue(struct nvme_queue *nvmeq, int qid, bool polled)
 	return result;
 }
 
+#ifdef CONFIG_DMABUF_TOKEN
+static void nvme_dmabuf_invalidate_mappings(struct dma_buf_attachment *attach)
+{
+	struct io_dmabuf_token *token = attach->importer_priv;
+
+	io_dmabuf_token_invalidate_mappings(token);
+}
+
+const struct dma_buf_attach_ops nvme_dmabuf_importer_ops = {
+	.invalidate_mappings	= nvme_dmabuf_invalidate_mappings,
+	.allow_peer2peer	= true,
+};
+
+static struct io_dmabuf_map *nvme_dmabuf_token_map(struct io_dmabuf_token *token)
+{
+	struct nvme_dmabuf_token *data = token->dev_priv;
+	struct dma_buf_attachment *attach = data->attach;
+	dma_addr_t *dma_list = NULL;
+	unsigned long tmp, i = 0;
+	struct nvme_dmabuf_map *map;
+	struct scatterlist *sg;
+	struct sg_table *sgt;
+	unsigned nr_entries;
+	int ret;
+
+	dma_resv_assert_held(token->dmabuf->resv);
+
+	map = kmalloc(sizeof(*map), GFP_KERNEL);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	nr_entries = token->dmabuf->size / NVME_CTRL_PAGE_SIZE;
+	dma_list = kmalloc_array(nr_entries, sizeof(dma_list[0]), GFP_KERNEL);
+	if (!dma_list) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	sgt = dma_buf_map_attachment(attach, token->dir);
+	if (IS_ERR(sgt)) {
+		ret = PTR_ERR(sgt);
+		sgt = NULL;
+		goto err;
+	}
+
+	for_each_sgtable_dma_sg(sgt, sg, tmp) {
+		dma_addr_t dma_addr = sg_dma_address(sg);
+		unsigned long sg_len = sg_dma_len(sg);
+
+		if (sg_len % NVME_CTRL_PAGE_SIZE) {
+			ret = -EINVAL;
+			goto err;
+		}
+
+		while (sg_len) {
+			dma_list[i++] = dma_addr;
+			dma_addr += NVME_CTRL_PAGE_SIZE;
+			sg_len -= NVME_CTRL_PAGE_SIZE;
+		}
+	}
+
+	ret = io_dmabuf_init_map(token, &map->base);
+	if (ret)
+		goto err;
+	map->nr_entries = nr_entries;
+	map->dma_list = dma_list;
+	map->sgt = sgt;
+	return &map->base;
+err:
+	if (sgt)
+		dma_buf_unmap_attachment(attach, sgt, token->dir);
+	kfree(map);
+	kfree(dma_list);
+	return ERR_PTR(ret);
+}
+
+static void nvme_dmabuf_token_unmap(struct io_dmabuf_token *token,
+				 struct io_dmabuf_map *map_base)
+{
+	struct nvme_dmabuf_token *data = token->dev_priv;
+	struct nvme_dmabuf_map *map = container_of(map_base,
+						struct nvme_dmabuf_map, base);
+
+	dma_resv_assert_held(token->dmabuf->resv);
+
+	dma_buf_unmap_attachment(data->attach, map->sgt, token->dir);
+	kfree(map->dma_list);
+}
+
+static void nvme_dmabuf_token_release(struct io_dmabuf_token *token)
+{
+	struct nvme_dmabuf_token *data = token->dev_priv;
+
+	dma_buf_detach(token->dmabuf, data->attach);
+	kfree(data);
+}
+
+const struct io_dmabuf_token_dev_ops nvme_dma_token_ops = {
+	.map		= nvme_dmabuf_token_map,
+	.unmap		= nvme_dmabuf_token_unmap,
+	.release	= nvme_dmabuf_token_release,
+};
+
+static int nvme_create_dmabuf_token(struct request_queue *q,
+				 struct io_dmabuf_token *token)
+{
+	struct nvme_dmabuf_token *data;
+	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;
+
+	data = kzalloc(sizeof(data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	token->dev_priv = data;
+	token->dev_ops = &nvme_dma_token_ops;
+
+	attach = dma_buf_dynamic_attach(dmabuf, dev->dev,
+					&nvme_dmabuf_importer_ops, token);
+	if (IS_ERR(attach))
+		return PTR_ERR(attach);
+	data->attach = attach;
+	return 0;
+}
+#endif
+
 static const struct blk_mq_ops nvme_mq_admin_ops = {
 	.queue_rq	= nvme_queue_rq,
 	.complete	= nvme_pci_complete_rq,
@@ -2256,6 +2533,10 @@ static const struct blk_mq_ops nvme_mq_ops = {
 	.map_queues	= nvme_pci_map_queues,
 	.timeout	= nvme_timeout,
 	.poll		= nvme_poll,
+
+#ifdef CONFIG_DMABUF_TOKEN
+	.create_dmabuf_token = nvme_create_dmabuf_token,
+#endif
 };
 
 static void nvme_dev_remove_admin(struct nvme_dev *dev)
@@ -4289,5 +4570,6 @@ MODULE_AUTHOR("Matthew Wilcox <willy@linux.intel.com>");
 MODULE_LICENSE("GPL");
 MODULE_VERSION("1.0");
 MODULE_DESCRIPTION("NVMe host PCIe transport driver");
+MODULE_IMPORT_NS("DMA_BUF");
 module_init(nvme_init);
 module_exit(nvme_exit);
-- 
2.53.0