OSCL-LXR linux-6.0.1/​drivers/​pci/​p2pdma.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * PCI Peer 2 Peer DMA support.
  *
  * Copyright (c) 2016-2018, Logan Gunthorpe
  * Copyright (c) 2016-2017, Microsemi Corporation
  * Copyright (c) 2017, Christoph Hellwig
  * Copyright (c) 2018, Eideticom Inc.
  */
 
 #define pr_fmt(fmt) "pci-p2pdma: " fmt
 #include <linux/ctype.h>
 #include <linux/dma-map-ops.h>
 #include <linux/pci-p2pdma.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/genalloc.h>
 #include <linux/memremap.h>
 #include <linux/percpu-refcount.h>
 #include <linux/random.h>
 #include <linux/seq_buf.h>
 #include <linux/xarray.h>
 
 struct pci_p2pdma {
     struct gen_pool *pool;
     bool p2pmem_published;
     struct xarray map_types;
 };
 
 struct pci_p2pdma_pagemap {
     struct dev_pagemap pgmap;
     struct pci_dev *provider;
     u64 bus_offset;
 };
 
 static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
 {
     return container_of(pgmap, struct pci_p2pdma_pagemap, pgmap);
 }
 
 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
              char *buf)
 {
     struct pci_dev *pdev = to_pci_dev(dev);
     struct pci_p2pdma *p2pdma;
     size_t size = 0;
 
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     if (p2pdma && p2pdma->pool)
         size = gen_pool_size(p2pdma->pool);
     rcu_read_unlock();
 
     return sysfs_emit(buf, "%zd\n", size);
 }
 static DEVICE_ATTR_RO(size);
 
 static ssize_t available_show(struct device *dev, struct device_attribute *attr,
                   char *buf)
 {
     struct pci_dev *pdev = to_pci_dev(dev);
     struct pci_p2pdma *p2pdma;
     size_t avail = 0;
 
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     if (p2pdma && p2pdma->pool)
         avail = gen_pool_avail(p2pdma->pool);
     rcu_read_unlock();
 
     return sysfs_emit(buf, "%zd\n", avail);
 }
 static DEVICE_ATTR_RO(available);
 
 static ssize_t published_show(struct device *dev, struct device_attribute *attr,
                   char *buf)
 {
     struct pci_dev *pdev = to_pci_dev(dev);
     struct pci_p2pdma *p2pdma;
     bool published = false;
 
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     if (p2pdma)
         published = p2pdma->p2pmem_published;
     rcu_read_unlock();
 
     return sysfs_emit(buf, "%d\n", published);
 }
 static DEVICE_ATTR_RO(published);
 
 static struct attribute *p2pmem_attrs[] = {
     &dev_attr_size.attr,
     &dev_attr_available.attr,
     &dev_attr_published.attr,
     NULL,
 };
 
 static const struct attribute_group p2pmem_group = {
     .attrs = p2pmem_attrs,
     .name = "p2pmem",
 };
 
 static void pci_p2pdma_release(void *data)
 {
     struct pci_dev *pdev = data;
     struct pci_p2pdma *p2pdma;
 
     p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
     if (!p2pdma)
         return;
 
     /* Flush and disable pci_alloc_p2p_mem() */
     pdev->p2pdma = NULL;
     synchronize_rcu();
 
     gen_pool_destroy(p2pdma->pool);
     sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
     xa_destroy(&p2pdma->map_types);
 }
 
 static int pci_p2pdma_setup(struct pci_dev *pdev)
 {
     int error = -ENOMEM;
     struct pci_p2pdma *p2p;
 
     p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
     if (!p2p)
         return -ENOMEM;
 
     xa_init(&p2p->map_types);
 
     p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
     if (!p2p->pool)
         goto out;
 
     error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
     if (error)
         goto out_pool_destroy;
 
     error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
     if (error)
         goto out_pool_destroy;
 
     rcu_assign_pointer(pdev->p2pdma, p2p);
     return 0;
 
 out_pool_destroy:
     gen_pool_destroy(p2p->pool);
 out:
     devm_kfree(&pdev->dev, p2p);
     return error;
 }
 
 /**
  * pci_p2pdma_add_resource - add memory for use as p2p memory
  * @pdev: the device to add the memory to
  * @bar: PCI BAR to add
  * @size: size of the memory to add, may be zero to use the whole BAR
  * @offset: offset into the PCI BAR
  *
  * The memory will be given ZONE_DEVICE struct pages so that it may
  * be used with any DMA request.
  */
 int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
                 u64 offset)
 {
     struct pci_p2pdma_pagemap *p2p_pgmap;
     struct dev_pagemap *pgmap;
     struct pci_p2pdma *p2pdma;
     void *addr;
     int error;
 
     if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
         return -EINVAL;
 
     if (offset >= pci_resource_len(pdev, bar))
         return -EINVAL;
 
     if (!size)
         size = pci_resource_len(pdev, bar) - offset;
 
     if (size + offset > pci_resource_len(pdev, bar))
         return -EINVAL;
 
     if (!pdev->p2pdma) {
         error = pci_p2pdma_setup(pdev);
         if (error)
             return error;
     }
 
     p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
     if (!p2p_pgmap)
         return -ENOMEM;
 
     pgmap = &p2p_pgmap->pgmap;
     pgmap->range.start = pci_resource_start(pdev, bar) + offset;
     pgmap->range.end = pgmap->range.start + size - 1;
     pgmap->nr_range = 1;
     pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
 
     p2p_pgmap->provider = pdev;
     p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -
         pci_resource_start(pdev, bar);
 
     addr = devm_memremap_pages(&pdev->dev, pgmap);
     if (IS_ERR(addr)) {
         error = PTR_ERR(addr);
         goto pgmap_free;
     }
 
     p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
     error = gen_pool_add_owner(p2pdma->pool, (unsigned long)addr,
             pci_bus_address(pdev, bar) + offset,
             range_len(&pgmap->range), dev_to_node(&pdev->dev),
             &pgmap->ref);
     if (error)
         goto pages_free;
 
     pci_info(pdev, "added peer-to-peer DMA memory %#llx-%#llx\n",
          pgmap->range.start, pgmap->range.end);
 
     return 0;
 
 pages_free:
     devm_memunmap_pages(&pdev->dev, pgmap);
 pgmap_free:
     devm_kfree(&pdev->dev, pgmap);
     return error;
 }
 EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
 
 /*
  * Note this function returns the parent PCI device with a
  * reference taken. It is the caller's responsibility to drop
  * the reference.
  */
 static struct pci_dev *find_parent_pci_dev(struct device *dev)
 {
     struct device *parent;
 
     dev = get_device(dev);
 
     while (dev) {
         if (dev_is_pci(dev))
             return to_pci_dev(dev);
 
         parent = get_device(dev->parent);
         put_device(dev);
         dev = parent;
     }
 
     return NULL;
 }
 
 /*
  * Check if a PCI bridge has its ACS redirection bits set to redirect P2P
  * TLPs upstream via ACS. Returns 1 if the packets will be redirected
  * upstream, 0 otherwise.
  */
 static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
 {
     int pos;
     u16 ctrl;
 
     pos = pdev->acs_cap;
     if (!pos)
         return 0;
 
     pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
 
     if (ctrl & (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC))
         return 1;
 
     return 0;
 }
 
 static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
 {
     if (!buf)
         return;
 
     seq_buf_printf(buf, "%s;", pci_name(pdev));
 }
 
 static bool cpu_supports_p2pdma(void)
 {
 #ifdef CONFIG_X86
     struct cpuinfo_x86 *c = &cpu_data(0);
 
     /* Any AMD CPU whose family ID is Zen or newer supports p2pdma */
     if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17)
         return true;
 #endif
 
     return false;
 }
 
 static const struct pci_p2pdma_whitelist_entry {
     unsigned short vendor;
     unsigned short device;
     enum {
         REQ_SAME_HOST_BRIDGE    = 1 << 0,
     } flags;
 } pci_p2pdma_whitelist[] = {
     /* Intel Xeon E5/Core i7 */
     {PCI_VENDOR_ID_INTEL,   0x3c00, REQ_SAME_HOST_BRIDGE},
     {PCI_VENDOR_ID_INTEL,   0x3c01, REQ_SAME_HOST_BRIDGE},
     /* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */
     {PCI_VENDOR_ID_INTEL,   0x2f00, REQ_SAME_HOST_BRIDGE},
     {PCI_VENDOR_ID_INTEL,   0x2f01, REQ_SAME_HOST_BRIDGE},
     /* Intel SkyLake-E */
     {PCI_VENDOR_ID_INTEL,   0x2030, 0},
     {PCI_VENDOR_ID_INTEL,   0x2031, 0},
     {PCI_VENDOR_ID_INTEL,   0x2032, 0},
     {PCI_VENDOR_ID_INTEL,   0x2033, 0},
     {PCI_VENDOR_ID_INTEL,   0x2020, 0},
     {PCI_VENDOR_ID_INTEL,   0x09a2, 0},
     {}
 };
 
 /*
  * If the first device on host's root bus is either devfn 00.0 or a PCIe
  * Root Port, return it.  Otherwise return NULL.
  *
  * We often use a devfn 00.0 "host bridge" in the pci_p2pdma_whitelist[]
  * (though there is no PCI/PCIe requirement for such a device).  On some
  * platforms, e.g., Intel Skylake, there is no such host bridge device, and
  * pci_p2pdma_whitelist[] may contain a Root Port at any devfn.
  *
  * This function is similar to pci_get_slot(host->bus, 0), but it does
  * not take the pci_bus_sem lock since __host_bridge_whitelist() must not
  * sleep.
  *
  * For this to be safe, the caller should hold a reference to a device on the
  * bridge, which should ensure the host_bridge device will not be freed
  * or removed from the head of the devices list.
  */
 static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
 {
     struct pci_dev *root;
 
     root = list_first_entry_or_null(&host->bus->devices,
                     struct pci_dev, bus_list);
 
     if (!root)
         return NULL;
 
     if (root->devfn == PCI_DEVFN(0, 0))
         return root;
 
     if (pci_pcie_type(root) == PCI_EXP_TYPE_ROOT_PORT)
         return root;
 
     return NULL;
 }
 
 static bool __host_bridge_whitelist(struct pci_host_bridge *host,
                     bool same_host_bridge, bool warn)
 {
     struct pci_dev *root = pci_host_bridge_dev(host);
     const struct pci_p2pdma_whitelist_entry *entry;
     unsigned short vendor, device;
 
     if (!root)
         return false;
 
     vendor = root->vendor;
     device = root->device;
 
     for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
         if (vendor != entry->vendor || device != entry->device)
             continue;
         if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)
             return false;
 
         return true;
     }
 
     if (warn)
         pci_warn(root, "Host bridge not in P2PDMA whitelist: %04x:%04x\n",
              vendor, device);
 
     return false;
 }
 
 /*
  * If we can't find a common upstream bridge take a look at the root
  * complex and compare it to a whitelist of known good hardware.
  */
 static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,
                   bool warn)
 {
     struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
     struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
 
     if (host_a == host_b)
         return __host_bridge_whitelist(host_a, true, warn);
 
     if (__host_bridge_whitelist(host_a, false, warn) &&
         __host_bridge_whitelist(host_b, false, warn))
         return true;
 
     return false;
 }
 
 static unsigned long map_types_idx(struct pci_dev *client)
 {
     return (pci_domain_nr(client->bus) << 16) |
         (client->bus->number << 8) | client->devfn;
 }
 
 /*
  * Calculate the P2PDMA mapping type and distance between two PCI devices.
  *
  * If the two devices are the same PCI function, return
  * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0.
  *
  * If they are two functions of the same device, return
  * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge,
  * then one hop back down to another function of the same device).
  *
  * In the case where two devices are connected to the same PCIe switch,
  * return a distance of 4. This corresponds to the following PCI tree:
  *
  *     -+  Root Port
  *      \+ Switch Upstream Port
  *       +-+ Switch Downstream Port 0
  *       + \- Device A
  *       \-+ Switch Downstream Port 1
  *         \- Device B
  *
  * The distance is 4 because we traverse from Device A to Downstream Port 0
  * to the common Switch Upstream Port, back down to Downstream Port 1 and
  * then to Device B. The mapping type returned depends on the ACS
  * redirection setting of the ports along the path.
  *
  * If ACS redirect is set on any port in the path, traffic between the
  * devices will go through the host bridge, so return
  * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return
  * PCI_P2PDMA_MAP_BUS_ADDR.
  *
  * Any two devices that have a data path that goes through the host bridge
  * will consult a whitelist. If the host bridge is in the whitelist, return
  * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of
  * ports per above. If the device is not in the whitelist, return
  * PCI_P2PDMA_MAP_NOT_SUPPORTED.
  */
 static enum pci_p2pdma_map_type
 calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
         int *dist, bool verbose)
 {
     enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
     struct pci_dev *a = provider, *b = client, *bb;
     bool acs_redirects = false;
     struct pci_p2pdma *p2pdma;
     struct seq_buf acs_list;
     int acs_cnt = 0;
     int dist_a = 0;
     int dist_b = 0;
     char buf[128];
 
     seq_buf_init(&acs_list, buf, sizeof(buf));
 
     /*
      * Note, we don't need to take references to devices returned by
      * pci_upstream_bridge() seeing we hold a reference to a child
      * device which will already hold a reference to the upstream bridge.
      */
     while (a) {
         dist_b = 0;
 
         if (pci_bridge_has_acs_redir(a)) {
             seq_buf_print_bus_devfn(&acs_list, a);
             acs_cnt++;
         }
 
         bb = b;
 
         while (bb) {
             if (a == bb)
                 goto check_b_path_acs;
 
             bb = pci_upstream_bridge(bb);
             dist_b++;
         }
 
         a = pci_upstream_bridge(a);
         dist_a++;
     }
 
     *dist = dist_a + dist_b;
     goto map_through_host_bridge;
 
 check_b_path_acs:
     bb = b;
 
     while (bb) {
         if (a == bb)
             break;
 
         if (pci_bridge_has_acs_redir(bb)) {
             seq_buf_print_bus_devfn(&acs_list, bb);
             acs_cnt++;
         }
 
         bb = pci_upstream_bridge(bb);
     }
 
     *dist = dist_a + dist_b;
 
     if (!acs_cnt) {
         map_type = PCI_P2PDMA_MAP_BUS_ADDR;
         goto done;
     }
 
     if (verbose) {
         acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
         pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
              pci_name(provider));
         pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
              acs_list.buffer);
     }
     acs_redirects = true;
 
 map_through_host_bridge:
     if (!cpu_supports_p2pdma() &&
         !host_bridge_whitelist(provider, client, acs_redirects)) {
         if (verbose)
             pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n",
                  pci_name(provider));
         map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
     }
 done:
     rcu_read_lock();
     p2pdma = rcu_dereference(provider->p2pdma);
     if (p2pdma)
         xa_store(&p2pdma->map_types, map_types_idx(client),
              xa_mk_value(map_type), GFP_KERNEL);
     rcu_read_unlock();
     return map_type;
 }
 
 /**
  * pci_p2pdma_distance_many - Determine the cumulative distance between
  *  a p2pdma provider and the clients in use.
  * @provider: p2pdma provider to check against the client list
  * @clients: array of devices to check (NULL-terminated)
  * @num_clients: number of clients in the array
  * @verbose: if true, print warnings for devices when we return -1
  *
  * Returns -1 if any of the clients are not compatible, otherwise returns a
  * positive number where a lower number is the preferable choice. (If there's
  * one client that's the same as the provider it will return 0, which is best
  * choice).
  *
  * "compatible" means the provider and the clients are either all behind
  * the same PCI root port or the host bridges connected to each of the devices
  * are listed in the 'pci_p2pdma_whitelist'.
  */
 int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
                  int num_clients, bool verbose)
 {
     enum pci_p2pdma_map_type map;
     bool not_supported = false;
     struct pci_dev *pci_client;
     int total_dist = 0;
     int i, distance;
 
     if (num_clients == 0)
         return -1;
 
     for (i = 0; i < num_clients; i++) {
         pci_client = find_parent_pci_dev(clients[i]);
         if (!pci_client) {
             if (verbose)
                 dev_warn(clients[i],
                      "cannot be used for peer-to-peer DMA as it is not a PCI device\n");
             return -1;
         }
 
         map = calc_map_type_and_dist(provider, pci_client, &distance,
                          verbose);
 
         pci_dev_put(pci_client);
 
         if (map == PCI_P2PDMA_MAP_NOT_SUPPORTED)
             not_supported = true;
 
         if (not_supported && !verbose)
             break;
 
         total_dist += distance;
     }
 
     if (not_supported)
         return -1;
 
     return total_dist;
 }
 EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
 
 /**
  * pci_has_p2pmem - check if a given PCI device has published any p2pmem
  * @pdev: PCI device to check
  */
 bool pci_has_p2pmem(struct pci_dev *pdev)
 {
     struct pci_p2pdma *p2pdma;
     bool res;
 
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     res = p2pdma && p2pdma->p2pmem_published;
     rcu_read_unlock();
 
     return res;
 }
 EXPORT_SYMBOL_GPL(pci_has_p2pmem);
 
 /**
  * pci_p2pmem_find_many - find a peer-to-peer DMA memory device compatible with
  *  the specified list of clients and shortest distance (as determined
  *  by pci_p2pmem_dma())
  * @clients: array of devices to check (NULL-terminated)
  * @num_clients: number of client devices in the list
  *
  * If multiple devices are behind the same switch, the one "closest" to the
  * client devices in use will be chosen first. (So if one of the providers is
  * the same as one of the clients, that provider will be used ahead of any
  * other providers that are unrelated). If multiple providers are an equal
  * distance away, one will be chosen at random.
  *
  * Returns a pointer to the PCI device with a reference taken (use pci_dev_put
  * to return the reference) or NULL if no compatible device is found. The
  * found provider will also be assigned to the client list.
  */
 struct pci_dev *pci_p2pmem_find_many(struct device **clients, int num_clients)
 {
     struct pci_dev *pdev = NULL;
     int distance;
     int closest_distance = INT_MAX;
     struct pci_dev **closest_pdevs;
     int dev_cnt = 0;
     const int max_devs = PAGE_SIZE / sizeof(*closest_pdevs);
     int i;
 
     closest_pdevs = kmalloc(PAGE_SIZE, GFP_KERNEL);
     if (!closest_pdevs)
         return NULL;
 
     while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev))) {
         if (!pci_has_p2pmem(pdev))
             continue;
 
         distance = pci_p2pdma_distance_many(pdev, clients,
                             num_clients, false);
         if (distance < 0 || distance > closest_distance)
             continue;
 
         if (distance == closest_distance && dev_cnt >= max_devs)
             continue;
 
         if (distance < closest_distance) {
             for (i = 0; i < dev_cnt; i++)
                 pci_dev_put(closest_pdevs[i]);
 
             dev_cnt = 0;
             closest_distance = distance;
         }
 
         closest_pdevs[dev_cnt++] = pci_dev_get(pdev);
     }
 
     if (dev_cnt)
         pdev = pci_dev_get(closest_pdevs[prandom_u32_max(dev_cnt)]);
 
     for (i = 0; i < dev_cnt; i++)
         pci_dev_put(closest_pdevs[i]);
 
     kfree(closest_pdevs);
     return pdev;
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_find_many);
 
 /**
  * pci_alloc_p2pmem - allocate peer-to-peer DMA memory
  * @pdev: the device to allocate memory from
  * @size: number of bytes to allocate
  *
  * Returns the allocated memory or NULL on error.
  */
 void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
 {
     void *ret = NULL;
     struct percpu_ref *ref;
     struct pci_p2pdma *p2pdma;
 
     /*
      * Pairs with synchronize_rcu() in pci_p2pdma_release() to
      * ensure pdev->p2pdma is non-NULL for the duration of the
      * read-lock.
      */
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     if (unlikely(!p2pdma))
         goto out;
 
     ret = (void *)gen_pool_alloc_owner(p2pdma->pool, size, (void **) &ref);
     if (!ret)
         goto out;
 
     if (unlikely(!percpu_ref_tryget_live_rcu(ref))) {
         gen_pool_free(p2pdma->pool, (unsigned long) ret, size);
         ret = NULL;
         goto out;
     }
 out:
     rcu_read_unlock();
     return ret;
 }
 EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
 
 /**
  * pci_free_p2pmem - free peer-to-peer DMA memory
  * @pdev: the device the memory was allocated from
  * @addr: address of the memory that was allocated
  * @size: number of bytes that were allocated
  */
 void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
 {
     struct percpu_ref *ref;
     struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
 
     gen_pool_free_owner(p2pdma->pool, (uintptr_t)addr, size,
             (void **) &ref);
     percpu_ref_put(ref);
 }
 EXPORT_SYMBOL_GPL(pci_free_p2pmem);
 
 /**
  * pci_p2pmem_virt_to_bus - return the PCI bus address for a given virtual
  *  address obtained with pci_alloc_p2pmem()
  * @pdev: the device the memory was allocated from
  * @addr: address of the memory that was allocated
  */
 pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
 {
     struct pci_p2pdma *p2pdma;
 
     if (!addr)
         return 0;
 
     p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
     if (!p2pdma)
         return 0;
 
     /*
      * Note: when we added the memory to the pool we used the PCI
      * bus address as the physical address. So gen_pool_virt_to_phys()
      * actually returns the bus address despite the misleading name.
      */
     return gen_pool_virt_to_phys(p2pdma->pool, (unsigned long)addr);
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
 
 /**
  * pci_p2pmem_alloc_sgl - allocate peer-to-peer DMA memory in a scatterlist
  * @pdev: the device to allocate memory from
  * @nents: the number of SG entries in the list
  * @length: number of bytes to allocate
  *
  * Return: %NULL on error or &struct scatterlist pointer and @nents on success
  */
 struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
                      unsigned int *nents, u32 length)
 {
     struct scatterlist *sg;
     void *addr;
 
     sg = kmalloc(sizeof(*sg), GFP_KERNEL);
     if (!sg)
         return NULL;
 
     sg_init_table(sg, 1);
 
     addr = pci_alloc_p2pmem(pdev, length);
     if (!addr)
         goto out_free_sg;
 
     sg_set_buf(sg, addr, length);
     *nents = 1;
     return sg;
 
 out_free_sg:
     kfree(sg);
     return NULL;
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_alloc_sgl);
 
 /**
  * pci_p2pmem_free_sgl - free a scatterlist allocated by pci_p2pmem_alloc_sgl()
  * @pdev: the device to allocate memory from
  * @sgl: the allocated scatterlist
  */
 void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl)
 {
     struct scatterlist *sg;
     int count;
 
     for_each_sg(sgl, sg, INT_MAX, count) {
         if (!sg)
             break;
 
         pci_free_p2pmem(pdev, sg_virt(sg), sg->length);
     }
     kfree(sgl);
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
 
 /**
  * pci_p2pmem_publish - publish the peer-to-peer DMA memory for use by
  *  other devices with pci_p2pmem_find()
  * @pdev: the device with peer-to-peer DMA memory to publish
  * @publish: set to true to publish the memory, false to unpublish it
  *
  * Published memory can be used by other PCI device drivers for
  * peer-2-peer DMA operations. Non-published memory is reserved for
  * exclusive use of the device driver that registers the peer-to-peer
  * memory.
  */
 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 {
     struct pci_p2pdma *p2pdma;
 
     rcu_read_lock();
     p2pdma = rcu_dereference(pdev->p2pdma);
     if (p2pdma)
         p2pdma->p2pmem_published = publish;
     rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 
 static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
                             struct device *dev)
 {
     enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
     struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
     struct pci_dev *client;
     struct pci_p2pdma *p2pdma;
     int dist;
 
     if (!provider->p2pdma)
         return PCI_P2PDMA_MAP_NOT_SUPPORTED;
 
     if (!dev_is_pci(dev))
         return PCI_P2PDMA_MAP_NOT_SUPPORTED;
 
     client = to_pci_dev(dev);
 
     rcu_read_lock();
     p2pdma = rcu_dereference(provider->p2pdma);
 
     if (p2pdma)
         type = xa_to_value(xa_load(&p2pdma->map_types,
                        map_types_idx(client)));
     rcu_read_unlock();
 
     if (type == PCI_P2PDMA_MAP_UNKNOWN)
         return calc_map_type_and_dist(provider, client, &dist, true);
 
     return type;
 }
 
 /**
  * pci_p2pdma_map_segment - map an sg segment determining the mapping type
  * @state: State structure that should be declared outside of the for_each_sg()
  *  loop and initialized to zero.
  * @dev: DMA device that's doing the mapping operation
  * @sg: scatterlist segment to map
  *
  * This is a helper to be used by non-IOMMU dma_map_sg() implementations where
  * the sg segment is the same for the page_link and the dma_address.
  *
  * Attempt to map a single segment in an SGL with the PCI bus address.
  * The segment must point to a PCI P2PDMA page and thus must be
  * wrapped in a is_pci_p2pdma_page(sg_page(sg)) check.
  *
  * Returns the type of mapping used and maps the page if the type is
  * PCI_P2PDMA_MAP_BUS_ADDR.
  */
 enum pci_p2pdma_map_type
 pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
                struct scatterlist *sg)
 {
     if (state->pgmap != sg_page(sg)->pgmap) {
         state->pgmap = sg_page(sg)->pgmap;
         state->map = pci_p2pdma_map_type(state->pgmap, dev);
         state->bus_off = to_p2p_pgmap(state->pgmap)->bus_offset;
     }
 
     if (state->map == PCI_P2PDMA_MAP_BUS_ADDR) {
         sg->dma_address = sg_phys(sg) + state->bus_off;
         sg_dma_len(sg) = sg->length;
         sg_dma_mark_bus_address(sg);
     }
 
     return state->map;
 }
 
 /**
  * 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 its full BDF device
  * name) or a boolean (in any format kstrtobool() 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 kstrtobool 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 (!kstrtobool(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 p2pdma 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);

This page was automatically generated by the 2.1.0 LXR engine. The LXR team