diff options
Diffstat (limited to 'drivers/pci/p2pdma.c')
| -rw-r--r-- | drivers/pci/p2pdma.c | 1113 |
1 files changed, 1113 insertions, 0 deletions
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c new file mode 100644 index 000000000..fa7370f95 --- /dev/null +++ b/drivers/pci/p2pdma.c @@ -0,0 +1,1113 @@ +// 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 int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj, + struct bin_attribute *attr, struct vm_area_struct *vma) +{ + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj)); + size_t len = vma->vm_end - vma->vm_start; + struct pci_p2pdma *p2pdma; + struct percpu_ref *ref; + unsigned long vaddr; + void *kaddr; + int ret; + + /* prevent private mappings from being established */ + if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) { + pci_info_ratelimited(pdev, + "%s: fail, attempted private mapping\n", + current->comm); + return -EINVAL; + } + + if (vma->vm_pgoff) { + pci_info_ratelimited(pdev, + "%s: fail, attempted mapping with non-zero offset\n", + current->comm); + return -EINVAL; + } + + rcu_read_lock(); + p2pdma = rcu_dereference(pdev->p2pdma); + if (!p2pdma) { + ret = -ENODEV; + goto out; + } + + kaddr = (void *)gen_pool_alloc_owner(p2pdma->pool, len, (void **)&ref); + if (!kaddr) { + ret = -ENOMEM; + goto out; + } + + /* + * vm_insert_page() can sleep, so a reference is taken to mapping + * such that rcu_read_unlock() can be done before inserting the + * pages + */ + if (unlikely(!percpu_ref_tryget_live_rcu(ref))) { + ret = -ENODEV; + goto out_free_mem; + } + rcu_read_unlock(); + + for (vaddr = vma->vm_start; vaddr < vma->vm_end; vaddr += PAGE_SIZE) { + ret = vm_insert_page(vma, vaddr, virt_to_page(kaddr)); + if (ret) { + gen_pool_free(p2pdma->pool, (uintptr_t)kaddr, len); + return ret; + } + percpu_ref_get(ref); + put_page(virt_to_page(kaddr)); + kaddr += PAGE_SIZE; + len -= PAGE_SIZE; + } + + percpu_ref_put(ref); + + return 0; +out_free_mem: + gen_pool_free(p2pdma->pool, (uintptr_t)kaddr, len); +out: + rcu_read_unlock(); + return ret; +} + +static struct bin_attribute p2pmem_alloc_attr = { + .attr = { .name = "allocate", .mode = 0660 }, + .mmap = p2pmem_alloc_mmap, + /* + * Some places where we want to call mmap (ie. python) will check + * that the file size is greater than the mmap size before allowing + * the mmap to continue. To work around this, just set the size + * to be very large. + */ + .size = SZ_1T, +}; + +static struct attribute *p2pmem_attrs[] = { + &dev_attr_size.attr, + &dev_attr_available.attr, + &dev_attr_published.attr, + NULL, +}; + +static struct bin_attribute *p2pmem_bin_attrs[] = { + &p2pmem_alloc_attr, + NULL, +}; + +static const struct attribute_group p2pmem_group = { + .attrs = p2pmem_attrs, + .bin_attrs = p2pmem_bin_attrs, + .name = "p2pmem", +}; + +static void p2pdma_page_free(struct page *page) +{ + struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(page->pgmap); + /* safe to dereference while a reference is held to the percpu ref */ + struct pci_p2pdma *p2pdma = + rcu_dereference_protected(pgmap->provider->p2pdma, 1); + struct percpu_ref *ref; + + gen_pool_free_owner(p2pdma->pool, (uintptr_t)page_to_virt(page), + PAGE_SIZE, (void **)&ref); + percpu_ref_put(ref); +} + +static const struct dev_pagemap_ops p2pdma_pgmap_ops = { + .page_free = p2pdma_page_free, +}; + +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; +} + +static void pci_p2pdma_unmap_mappings(void *data) +{ + struct pci_dev *pdev = data; + + /* + * Removing the alloc attribute from sysfs will call + * unmap_mapping_range() on the inode, teardown any existing userspace + * mappings and prevent new ones from being created. + */ + sysfs_remove_file_from_group(&pdev->dev.kobj, &p2pmem_alloc_attr.attr, + p2pmem_group.name); +} + +/** + * 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; + pgmap->ops = &p2pdma_pgmap_ops; + + 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; + } + + error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_unmap_mappings, + pdev); + if (error) + goto pages_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) | pci_dev_id(client); +} + +/* + * 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 + * @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; + + for_each_pci_dev(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[get_random_u32_below(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); |