nvme-pci: Add support for P2P memory in requests

For P2P requests, we must use the pci_p2pmem_map_sg() function instead of
the dma_map_sg functions.

With that, we can then indicate PCI_P2P support in the request queue.  For
this, we create an NVME_F_PCI_P2P flag which tells the core to set
QUEUE_FLAG_PCI_P2P in the request queue.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>

drivers/nvme/host/core.c

@@ -3051,7 +3051,11 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 	ns->queue = blk_mq_init_queue(ctrl->tagset);
 	if (IS_ERR(ns->queue))
 		goto out_free_ns;
+
 	blk_queue_flag_set(QUEUE_FLAG_NONROT, ns->queue);
+	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
+		blk_queue_flag_set(QUEUE_FLAG_PCI_P2PDMA, ns->queue);
+
 	ns->queue->queuedata = ns;
 	ns->ctrl = ctrl;
 

drivers/nvme/host/nvme.h

@@ -343,6 +343,7 @@ struct nvme_ctrl_ops {
 	unsigned int flags;
 #define NVME_F_FABRICS			(1 << 0)
 #define NVME_F_METADATA_SUPPORTED	(1 << 1)
+#define NVME_F_PCI_P2PDMA		(1 << 2)
 	int (*reg_read32)(struct nvme_ctrl *ctrl, u32 off, u32 *val);
 	int (*reg_write32)(struct nvme_ctrl *ctrl, u32 off, u32 val);
 	int (*reg_read64)(struct nvme_ctrl *ctrl, u32 off, u64 *val);

drivers/nvme/host/pci.c

@@ -745,8 +745,13 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 		goto out;
 
 	ret = BLK_STS_RESOURCE;
-	nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir,
-			DMA_ATTR_NO_WARN);
+
+	if (is_pci_p2pdma_page(sg_page(iod->sg)))
+		nr_mapped = pci_p2pdma_map_sg(dev->dev, iod->sg, iod->nents,
+					  dma_dir);
+	else
+		nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents,
+					     dma_dir,  DMA_ATTR_NO_WARN);
 	if (!nr_mapped)
 		goto out;
 
@@ -788,7 +793,10 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
 			DMA_TO_DEVICE : DMA_FROM_DEVICE;
 
 	if (iod->nents) {
-		dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
+		/* P2PDMA requests do not need to be unmapped */
+		if (!is_pci_p2pdma_page(sg_page(iod->sg)))
+			dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
+
 		if (blk_integrity_rq(req))
 			dma_unmap_sg(dev->dev, &iod->meta_sg, 1, dma_dir);
 	}
@@ -2400,7 +2408,8 @@ static int nvme_pci_get_address(struct nvme_ctrl *ctrl, char *buf, int size)
 static const struct nvme_ctrl_ops nvme_pci_ctrl_ops = {
 	.name			= "pcie",
 	.module			= THIS_MODULE,
-	.flags			= NVME_F_METADATA_SUPPORTED,
+	.flags			= NVME_F_METADATA_SUPPORTED |
+				  NVME_F_PCI_P2PDMA,
 	.reg_read32		= nvme_pci_reg_read32,
 	.reg_write32		= nvme_pci_reg_write32,
 	.reg_read64		= nvme_pci_reg_read64,