blob: ae3c5b25dcc7d0fb80cae736e8090c137edf3420 [file] [log] [blame]
// 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/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>
struct pci_p2pdma {
struct percpu_ref devmap_ref;
struct completion devmap_ref_done;
struct gen_pool *pool;
bool p2pmem_published;
};
static ssize_t size_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
size_t size = 0;
if (pdev->p2pdma->pool)
size = gen_pool_size(pdev->p2pdma->pool);
return snprintf(buf, PAGE_SIZE, "%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);
size_t avail = 0;
if (pdev->p2pdma->pool)
avail = gen_pool_avail(pdev->p2pdma->pool);
return snprintf(buf, PAGE_SIZE, "%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);
return snprintf(buf, PAGE_SIZE, "%d\n",
pdev->p2pdma->p2pmem_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_percpu_release(struct percpu_ref *ref)
{
struct pci_p2pdma *p2p =
container_of(ref, struct pci_p2pdma, devmap_ref);
complete_all(&p2p->devmap_ref_done);
}
static void pci_p2pdma_percpu_kill(void *data)
{
struct percpu_ref *ref = data;
/*
* pci_p2pdma_add_resource() may be called multiple times
* by a driver and may register the percpu_kill devm action multiple
* times. We only want the first action to actually kill the
* percpu_ref.
*/
if (percpu_ref_is_dying(ref))
return;
percpu_ref_kill(ref);
}
static void pci_p2pdma_release(void *data)
{
struct pci_dev *pdev = data;
if (!pdev->p2pdma)
return;
wait_for_completion(&pdev->p2pdma->devmap_ref_done);
percpu_ref_exit(&pdev->p2pdma->devmap_ref);
gen_pool_destroy(pdev->p2pdma->pool);
sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
pdev->p2pdma = NULL;
}
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;
p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
if (!p2p->pool)
goto out;
init_completion(&p2p->devmap_ref_done);
error = percpu_ref_init(&p2p->devmap_ref,
pci_p2pdma_percpu_release, 0, GFP_KERNEL);
if (error)
goto out_pool_destroy;
error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
if (error)
goto out_pool_destroy;
pdev->p2pdma = p2p;
error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
if (error)
goto out_pool_destroy;
return 0;
out_pool_destroy:
pdev->p2pdma = NULL;
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 dev_pagemap *pgmap;
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;
}
pgmap = devm_kzalloc(&pdev->dev, sizeof(*pgmap), GFP_KERNEL);
if (!pgmap)
return -ENOMEM;
pgmap->res.start = pci_resource_start(pdev, bar) + offset;
pgmap->res.end = pgmap->res.start + size - 1;
pgmap->res.flags = pci_resource_flags(pdev, bar);
pgmap->ref = &pdev->p2pdma->devmap_ref;
pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
pgmap->pci_p2pdma_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 = gen_pool_add_virt(pdev->p2pdma->pool, (unsigned long)addr,
pci_bus_address(pdev, bar) + offset,
resource_size(&pgmap->res), dev_to_node(&pdev->dev));
if (error)
goto pgmap_free;
error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_percpu_kill,
&pdev->p2pdma->devmap_ref);
if (error)
goto pgmap_free;
pci_info(pdev, "added peer-to-peer DMA memory %pR\n",
&pgmap->res);
return 0;
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 responsibily 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 = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
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));
}
/*
* Find the distance through the nearest common upstream bridge between
* two PCI devices.
*
* If the two devices are the same device then 0 will be returned.
*
* If there are two virtual functions of the same device behind the same
* bridge port then 2 will be returned (one step down to the PCIe switch,
* then one step back to the same device).
*
* In the case where two devices are connected to the same PCIe switch, the
* value 4 will be returned. This corresponds to the following PCI tree:
*
* -+ Root Port
* \+ Switch Upstream Port
* +-+ Switch Downstream Port
* + \- Device A
* \-+ Switch Downstream Port
* \- Device B
*
* The distance is 4 because we traverse from Device A through the downstream
* port of the switch, to the common upstream port, back up to the second
* downstream port and then to Device B.
*
* Any two devices that don't have a common upstream bridge will return -1.
* In this way devices on separate PCIe root ports will be rejected, which
* is what we want for peer-to-peer seeing each PCIe root port defines a
* separate hierarchy domain and there's no way to determine whether the root
* complex supports forwarding between them.
*
* In the case where two devices are connected to different PCIe switches,
* this function will still return a positive distance as long as both
* switches eventually have a common upstream bridge. Note this covers
* the case of using multiple PCIe switches to achieve a desired level of
* fan-out from a root port. The exact distance will be a function of the
* number of switches between Device A and Device B.
*
* If a bridge which has any ACS redirection bits set is in the path
* then this functions will return -2. This is so we reject any
* cases where the TLPs are forwarded up into the root complex.
* In this case, a list of all infringing bridge addresses will be
* populated in acs_list (assuming it's non-null) for printk purposes.
*/
static int upstream_bridge_distance(struct pci_dev *a,
struct pci_dev *b,
struct seq_buf *acs_list)
{
int dist_a = 0;
int dist_b = 0;
struct pci_dev *bb = NULL;
int acs_cnt = 0;
/*
* 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++;
}
return -1;
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);
}
if (acs_cnt)
return -2;
return dist_a + dist_b;
}
static int upstream_bridge_distance_warn(struct pci_dev *provider,
struct pci_dev *client)
{
struct seq_buf acs_list;
int ret;
seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
if (!acs_list.buffer)
return -ENOMEM;
ret = upstream_bridge_distance(provider, client, &acs_list);
if (ret == -2) {
pci_warn(client, "cannot be used for peer-to-peer DMA as ACS redirect is set between the client and provider (%s)\n",
pci_name(provider));
/* Drop final semicolon */
acs_list.buffer[acs_list.len-1] = 0;
pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
acs_list.buffer);
} else if (ret < 0) {
pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge\n",
pci_name(provider));
}
kfree(acs_list.buffer);
return ret;
}
/**
* pci_p2pdma_distance_many - Determive 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 (behind the same
* root port as the provider), otherwise returns a positive number where
* a lower number is the preferrable choice. (If there's one client
* that's the same as the provider it will return 0, which is best choice).
*
* For now, "compatible" means the provider and the clients are all behind
* the same PCI root port. This cuts out cases that may work but is safest
* for the user. Future work can expand this to white-list root complexes that
* can safely forward between each ports.
*/
int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
int num_clients, bool verbose)
{
bool not_supported = false;
struct pci_dev *pci_client;
int distance = 0;
int i, ret;
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;
}
if (verbose)
ret = upstream_bridge_distance_warn(provider,
pci_client);
else
ret = upstream_bridge_distance(provider, pci_client,
NULL);
pci_dev_put(pci_client);
if (ret < 0)
not_supported = true;
if (not_supported && !verbose)
break;
distance += ret;
}
if (not_supported)
return -1;
return distance;
}
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)
{
return pdev->p2pdma && pdev->p2pdma->p2pmem_published;
}
EXPORT_SYMBOL_GPL(pci_has_p2pmem);
/**
* pci_p2pmem_find - 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 are
* 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_p2p_mem - 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;
if (unlikely(!pdev->p2pdma))
return NULL;
if (unlikely(!percpu_ref_tryget_live(&pdev->p2pdma->devmap_ref)))
return NULL;
ret = (void *)gen_pool_alloc(pdev->p2pdma->pool, size);
if (unlikely(!ret))
percpu_ref_put(&pdev->p2pdma->devmap_ref);
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 was allocated
*/
void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
{
gen_pool_free(pdev->p2pdma->pool, (uintptr_t)addr, size);
percpu_ref_put(&pdev->p2pdma->devmap_ref);
}
EXPORT_SYMBOL_GPL(pci_free_p2pmem);
/**
* pci_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)
{
if (!addr)
return 0;
if (!pdev->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(pdev->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
*
* Returns 0 on success
*/
struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
unsigned int *nents, u32 length)
{
struct scatterlist *sg;
void *addr;
sg = kzalloc(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
* exlusive use of the device driver that registers the peer-to-peer
* memory.
*/
void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
{
if (pdev->p2pdma)
pdev->p2pdma->p2pmem_published = publish;
}
EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
/**
* pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA
* @dev: device doing the DMA request
* @sg: scatter list to map
* @nents: elements in the scatterlist
* @dir: DMA direction
*
* Scatterlists mapped with this function should not be unmapped in any way.
*
* Returns the number of SG entries mapped or 0 on error.
*/
int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir)
{
struct dev_pagemap *pgmap;
struct scatterlist *s;
phys_addr_t paddr;
int i;
/*
* p2pdma mappings are not compatible with devices that use
* dma_virt_ops. If the upper layers do the right thing
* this should never happen because it will be prevented
* by the check in pci_p2pdma_add_client()
*/
if (WARN_ON_ONCE(IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
dev->dma_ops == &dma_virt_ops))
return 0;
for_each_sg(sg, s, nents, i) {
pgmap = sg_page(s)->pgmap;
paddr = sg_phys(s);
s->dma_address = paddr - pgmap->pci_p2pdma_bus_offset;
sg_dma_len(s) = s->length;
}
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);