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@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 09b3146c145c13c276e02dc8ef57eb6b8a6345f6..ae3c5b25dcc7d0fb80cae736e8090c137edf3420 100644 (file)
--- 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>
@@ -721,3 +723,83 @@ 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 b6dfb6dc2e5349b75b982dd907b9f448fd6589b5..bca9bc3e5be7929cad7eec9987f1089173351658 100644 (file)
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -32,6 +32,10 @@ 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)
@@ -82,6 +86,17 @@ 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 */