Date:   Tue, 25 Sep 2018 10:22:22 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian König <christian.koenig@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v7 04/13] PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers

Users of the P2PDMA infrastructure will typically need a way for
the user to tell the kernel to use P2P resources. Typically
this will be a simple on/off boolean operation but sometimes
it may be desirable for the user to specify the exact device to
use for the P2P operation.

Add new helpers for attributes which take a boolean or a PCI device.
Any boolean as accepted by strtobool() turn P2P on or off (such as 'y', 'n',
'1', '0', etc). Specifying a full PCI device name/BDF will select the
specific device.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/p2pdma.c       | 82 ++++++++++++++++++++++++++++++++++++++
 include/linux/pci-p2pdma.h | 15 +++++++
 2 files changed, 97 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index bbbf86165428..094d2b337c50 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -8,6 +8,8 @@
  * Copyright (c) 2018, Eideticom Inc.
  */
 
+#define pr_fmt(fmt) "pci-p2pdma: " fmt
+#include <linux/ctype.h>
 #include <linux/pci-p2pdma.h>
 #include <linux/module.h>
 #include <linux/slab.h>
@@ -859,3 +861,83 @@ int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 	return nents;
 }
 EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg);
+
+/**
+ * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
+ *		to enable p2pdma
+ * @page: contents of the value to be stored
+ * @p2p_dev: returns the PCI device that was selected to be used
+ *		(if one was specified in the stored value)
+ * @use_p2pdma: returns whether to enable p2pdma or not
+ *
+ * Parses an attribute value to decide whether to enable p2pdma.
+ * The value can select a PCI device (using it's full BDF device
+ * name) or a boolean (in any format strtobool() accepts). A false
+ * value disables p2pdma, a true value expects the caller
+ * to automatically find a compatible device and specifying a PCI device
+ * expects the caller to use the specific provider.
+ *
+ * pci_p2pdma_enable_show() should be used as the show operation for
+ * the attribute.
+ *
+ * Returns 0 on success
+ */
+int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
+			    bool *use_p2pdma)
+{
+	struct device *dev;
+
+	dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
+	if (dev) {
+		*use_p2pdma = true;
+		*p2p_dev = to_pci_dev(dev);
+
+		if (!pci_has_p2pmem(*p2p_dev)) {
+			pci_err(*p2p_dev,
+				"PCI device has no peer-to-peer memory: %s\n",
+				page);
+			pci_dev_put(*p2p_dev);
+			return -ENODEV;
+		}
+
+		return 0;
+	} else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
+		/*
+		 * If the user enters a PCI device that  doesn't exist
+		 * like "0000:01:00.1", we don't want strtobool to think
+		 * it's a '0' when it's clearly not what the user wanted.
+		 * So we require 0's and 1's to be exactly one character.
+		 */
+	} else if (!strtobool(page, use_p2pdma)) {
+		return 0;
+	}
+
+	pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
+	return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
+
+/**
+ * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
+ *		whether p2pdma is enabled
+ * @page: contents of the stored value
+ * @p2p_dev: the selected p2p device (NULL if no device is selected)
+ * @use_p2pdma: whether p2pdme has been enabled
+ *
+ * Attributes that use pci_p2pdma_enable_store() should use this function
+ * to show the value of the attribute.
+ *
+ * Returns 0 on success
+ */
+ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
+			       bool use_p2pdma)
+{
+	if (!use_p2pdma)
+		return sprintf(page, "0\n");
+
+	if (!p2p_dev)
+		return sprintf(page, "1\n");
+
+	return sprintf(page, "%s\n", pci_name(p2p_dev));
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index f039c48990a5..5248540eead2 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -37,6 +37,10 @@ void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl);
 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish);
 int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		      enum dma_data_direction dir);
+int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
+			    bool *use_p2pdma);
+ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
+			       bool use_p2pdma);
 #else /* CONFIG_PCI_P2PDMA */
 static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,
 		size_t size, u64 offset)
@@ -104,5 +108,16 @@ static inline int pci_p2pdma_map_sg(struct device *dev,
 {
 	return 0;
 }
+static inline int pci_p2pdma_enable_store(const char *page,
+		struct pci_dev **p2p_dev, bool *use_p2pdma)
+{
+	*use_p2pdma = false;
+	return 0;
+}
+static inline ssize_t pci_p2pdma_enable_show(char *page,
+		struct pci_dev *p2p_dev, bool use_p2pdma)
+{
+	return sprintf(page, "none\n");
+}
 #endif /* CONFIG_PCI_P2PDMA */
 #endif /* _LINUX_PCI_P2P_H */
-- 
2.19.0

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