linux/net/xdp/xsk_buff_pool.c
Magnus Karlsson f09ced4053 xsk: Fix race in SKB mode transmit with shared cq
Fix a race when multiple sockets are simultaneously calling sendto()
when the completion ring is shared in the SKB case. This is the case
when you share the same netdev and queue id through the
XDP_SHARED_UMEM bind flag. The problem is that multiple processes can
be in xsk_generic_xmit() and call the backpressure mechanism in
xskq_prod_reserve(xs->pool->cq). As this is a shared resource in this
specific scenario, a race might occur since the rings are
single-producer single-consumer.

Fix this by moving the tx_completion_lock from the socket to the pool
as the pool is shared between the sockets that share the completion
ring. (The pool is not shared when this is not the case.) And then
protect the accesses to xskq_prod_reserve() with this lock. The
tx_completion_lock is renamed cq_lock to better reflect that it
protects accesses to the potentially shared completion ring.

Fixes: 35fcde7f8d ("xsk: support for Tx")
Reported-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20201218134525.13119-2-magnus.karlsson@gmail.com
2020-12-18 16:10:21 +01:00

561 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <net/xsk_buff_pool.h>
#include <net/xdp_sock.h>
#include <net/xdp_sock_drv.h>
#include "xsk_queue.h"
#include "xdp_umem.h"
#include "xsk.h"
void xp_add_xsk(struct xsk_buff_pool *pool, struct xdp_sock *xs)
{
unsigned long flags;
if (!xs->tx)
return;
spin_lock_irqsave(&pool->xsk_tx_list_lock, flags);
list_add_rcu(&xs->tx_list, &pool->xsk_tx_list);
spin_unlock_irqrestore(&pool->xsk_tx_list_lock, flags);
}
void xp_del_xsk(struct xsk_buff_pool *pool, struct xdp_sock *xs)
{
unsigned long flags;
if (!xs->tx)
return;
spin_lock_irqsave(&pool->xsk_tx_list_lock, flags);
list_del_rcu(&xs->tx_list);
spin_unlock_irqrestore(&pool->xsk_tx_list_lock, flags);
}
void xp_destroy(struct xsk_buff_pool *pool)
{
if (!pool)
return;
kvfree(pool->heads);
kvfree(pool);
}
struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
struct xdp_umem *umem)
{
struct xsk_buff_pool *pool;
struct xdp_buff_xsk *xskb;
u32 i;
pool = kvzalloc(struct_size(pool, free_heads, umem->chunks),
GFP_KERNEL);
if (!pool)
goto out;
pool->heads = kvcalloc(umem->chunks, sizeof(*pool->heads), GFP_KERNEL);
if (!pool->heads)
goto out;
pool->chunk_mask = ~((u64)umem->chunk_size - 1);
pool->addrs_cnt = umem->size;
pool->heads_cnt = umem->chunks;
pool->free_heads_cnt = umem->chunks;
pool->headroom = umem->headroom;
pool->chunk_size = umem->chunk_size;
pool->unaligned = umem->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
pool->frame_len = umem->chunk_size - umem->headroom -
XDP_PACKET_HEADROOM;
pool->umem = umem;
pool->addrs = umem->addrs;
INIT_LIST_HEAD(&pool->free_list);
INIT_LIST_HEAD(&pool->xsk_tx_list);
spin_lock_init(&pool->xsk_tx_list_lock);
spin_lock_init(&pool->cq_lock);
refcount_set(&pool->users, 1);
pool->fq = xs->fq_tmp;
pool->cq = xs->cq_tmp;
for (i = 0; i < pool->free_heads_cnt; i++) {
xskb = &pool->heads[i];
xskb->pool = pool;
xskb->xdp.frame_sz = umem->chunk_size - umem->headroom;
pool->free_heads[i] = xskb;
}
return pool;
out:
xp_destroy(pool);
return NULL;
}
void xp_set_rxq_info(struct xsk_buff_pool *pool, struct xdp_rxq_info *rxq)
{
u32 i;
for (i = 0; i < pool->heads_cnt; i++)
pool->heads[i].xdp.rxq = rxq;
}
EXPORT_SYMBOL(xp_set_rxq_info);
static void xp_disable_drv_zc(struct xsk_buff_pool *pool)
{
struct netdev_bpf bpf;
int err;
ASSERT_RTNL();
if (pool->umem->zc) {
bpf.command = XDP_SETUP_XSK_POOL;
bpf.xsk.pool = NULL;
bpf.xsk.queue_id = pool->queue_id;
err = pool->netdev->netdev_ops->ndo_bpf(pool->netdev, &bpf);
if (err)
WARN(1, "Failed to disable zero-copy!\n");
}
}
static int __xp_assign_dev(struct xsk_buff_pool *pool,
struct net_device *netdev, u16 queue_id, u16 flags)
{
bool force_zc, force_copy;
struct netdev_bpf bpf;
int err = 0;
ASSERT_RTNL();
force_zc = flags & XDP_ZEROCOPY;
force_copy = flags & XDP_COPY;
if (force_zc && force_copy)
return -EINVAL;
if (xsk_get_pool_from_qid(netdev, queue_id))
return -EBUSY;
pool->netdev = netdev;
pool->queue_id = queue_id;
err = xsk_reg_pool_at_qid(netdev, pool, queue_id);
if (err)
return err;
if (flags & XDP_USE_NEED_WAKEUP)
pool->uses_need_wakeup = true;
/* Tx needs to be explicitly woken up the first time. Also
* for supporting drivers that do not implement this
* feature. They will always have to call sendto() or poll().
*/
pool->cached_need_wakeup = XDP_WAKEUP_TX;
dev_hold(netdev);
if (force_copy)
/* For copy-mode, we are done. */
return 0;
if (!netdev->netdev_ops->ndo_bpf ||
!netdev->netdev_ops->ndo_xsk_wakeup) {
err = -EOPNOTSUPP;
goto err_unreg_pool;
}
bpf.command = XDP_SETUP_XSK_POOL;
bpf.xsk.pool = pool;
bpf.xsk.queue_id = queue_id;
err = netdev->netdev_ops->ndo_bpf(netdev, &bpf);
if (err)
goto err_unreg_pool;
if (!pool->dma_pages) {
WARN(1, "Driver did not DMA map zero-copy buffers");
err = -EINVAL;
goto err_unreg_xsk;
}
pool->umem->zc = true;
return 0;
err_unreg_xsk:
xp_disable_drv_zc(pool);
err_unreg_pool:
if (!force_zc)
err = 0; /* fallback to copy mode */
if (err) {
xsk_clear_pool_at_qid(netdev, queue_id);
dev_put(netdev);
}
return err;
}
int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *dev,
u16 queue_id, u16 flags)
{
return __xp_assign_dev(pool, dev, queue_id, flags);
}
int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_umem *umem,
struct net_device *dev, u16 queue_id)
{
u16 flags;
/* One fill and completion ring required for each queue id. */
if (!pool->fq || !pool->cq)
return -EINVAL;
flags = umem->zc ? XDP_ZEROCOPY : XDP_COPY;
if (pool->uses_need_wakeup)
flags |= XDP_USE_NEED_WAKEUP;
return __xp_assign_dev(pool, dev, queue_id, flags);
}
void xp_clear_dev(struct xsk_buff_pool *pool)
{
if (!pool->netdev)
return;
xp_disable_drv_zc(pool);
xsk_clear_pool_at_qid(pool->netdev, pool->queue_id);
dev_put(pool->netdev);
pool->netdev = NULL;
}
static void xp_release_deferred(struct work_struct *work)
{
struct xsk_buff_pool *pool = container_of(work, struct xsk_buff_pool,
work);
rtnl_lock();
xp_clear_dev(pool);
rtnl_unlock();
if (pool->fq) {
xskq_destroy(pool->fq);
pool->fq = NULL;
}
if (pool->cq) {
xskq_destroy(pool->cq);
pool->cq = NULL;
}
xdp_put_umem(pool->umem, false);
xp_destroy(pool);
}
void xp_get_pool(struct xsk_buff_pool *pool)
{
refcount_inc(&pool->users);
}
bool xp_put_pool(struct xsk_buff_pool *pool)
{
if (!pool)
return false;
if (refcount_dec_and_test(&pool->users)) {
INIT_WORK(&pool->work, xp_release_deferred);
schedule_work(&pool->work);
return true;
}
return false;
}
static struct xsk_dma_map *xp_find_dma_map(struct xsk_buff_pool *pool)
{
struct xsk_dma_map *dma_map;
list_for_each_entry(dma_map, &pool->umem->xsk_dma_list, list) {
if (dma_map->netdev == pool->netdev)
return dma_map;
}
return NULL;
}
static struct xsk_dma_map *xp_create_dma_map(struct device *dev, struct net_device *netdev,
u32 nr_pages, struct xdp_umem *umem)
{
struct xsk_dma_map *dma_map;
dma_map = kzalloc(sizeof(*dma_map), GFP_KERNEL);
if (!dma_map)
return NULL;
dma_map->dma_pages = kvcalloc(nr_pages, sizeof(*dma_map->dma_pages), GFP_KERNEL);
if (!dma_map->dma_pages) {
kfree(dma_map);
return NULL;
}
dma_map->netdev = netdev;
dma_map->dev = dev;
dma_map->dma_need_sync = false;
dma_map->dma_pages_cnt = nr_pages;
refcount_set(&dma_map->users, 1);
list_add(&dma_map->list, &umem->xsk_dma_list);
return dma_map;
}
static void xp_destroy_dma_map(struct xsk_dma_map *dma_map)
{
list_del(&dma_map->list);
kvfree(dma_map->dma_pages);
kfree(dma_map);
}
static void __xp_dma_unmap(struct xsk_dma_map *dma_map, unsigned long attrs)
{
dma_addr_t *dma;
u32 i;
for (i = 0; i < dma_map->dma_pages_cnt; i++) {
dma = &dma_map->dma_pages[i];
if (*dma) {
dma_unmap_page_attrs(dma_map->dev, *dma, PAGE_SIZE,
DMA_BIDIRECTIONAL, attrs);
*dma = 0;
}
}
xp_destroy_dma_map(dma_map);
}
void xp_dma_unmap(struct xsk_buff_pool *pool, unsigned long attrs)
{
struct xsk_dma_map *dma_map;
if (pool->dma_pages_cnt == 0)
return;
dma_map = xp_find_dma_map(pool);
if (!dma_map) {
WARN(1, "Could not find dma_map for device");
return;
}
if (!refcount_dec_and_test(&dma_map->users))
return;
__xp_dma_unmap(dma_map, attrs);
kvfree(pool->dma_pages);
pool->dma_pages_cnt = 0;
pool->dev = NULL;
}
EXPORT_SYMBOL(xp_dma_unmap);
static void xp_check_dma_contiguity(struct xsk_dma_map *dma_map)
{
u32 i;
for (i = 0; i < dma_map->dma_pages_cnt - 1; i++) {
if (dma_map->dma_pages[i] + PAGE_SIZE == dma_map->dma_pages[i + 1])
dma_map->dma_pages[i] |= XSK_NEXT_PG_CONTIG_MASK;
else
dma_map->dma_pages[i] &= ~XSK_NEXT_PG_CONTIG_MASK;
}
}
static int xp_init_dma_info(struct xsk_buff_pool *pool, struct xsk_dma_map *dma_map)
{
pool->dma_pages = kvcalloc(dma_map->dma_pages_cnt, sizeof(*pool->dma_pages), GFP_KERNEL);
if (!pool->dma_pages)
return -ENOMEM;
pool->dev = dma_map->dev;
pool->dma_pages_cnt = dma_map->dma_pages_cnt;
pool->dma_need_sync = dma_map->dma_need_sync;
memcpy(pool->dma_pages, dma_map->dma_pages,
pool->dma_pages_cnt * sizeof(*pool->dma_pages));
return 0;
}
int xp_dma_map(struct xsk_buff_pool *pool, struct device *dev,
unsigned long attrs, struct page **pages, u32 nr_pages)
{
struct xsk_dma_map *dma_map;
dma_addr_t dma;
int err;
u32 i;
dma_map = xp_find_dma_map(pool);
if (dma_map) {
err = xp_init_dma_info(pool, dma_map);
if (err)
return err;
refcount_inc(&dma_map->users);
return 0;
}
dma_map = xp_create_dma_map(dev, pool->netdev, nr_pages, pool->umem);
if (!dma_map)
return -ENOMEM;
for (i = 0; i < dma_map->dma_pages_cnt; i++) {
dma = dma_map_page_attrs(dev, pages[i], 0, PAGE_SIZE,
DMA_BIDIRECTIONAL, attrs);
if (dma_mapping_error(dev, dma)) {
__xp_dma_unmap(dma_map, attrs);
return -ENOMEM;
}
if (dma_need_sync(dev, dma))
dma_map->dma_need_sync = true;
dma_map->dma_pages[i] = dma;
}
if (pool->unaligned)
xp_check_dma_contiguity(dma_map);
err = xp_init_dma_info(pool, dma_map);
if (err) {
__xp_dma_unmap(dma_map, attrs);
return err;
}
return 0;
}
EXPORT_SYMBOL(xp_dma_map);
static bool xp_addr_crosses_non_contig_pg(struct xsk_buff_pool *pool,
u64 addr)
{
return xp_desc_crosses_non_contig_pg(pool, addr, pool->chunk_size);
}
static bool xp_check_unaligned(struct xsk_buff_pool *pool, u64 *addr)
{
*addr = xp_unaligned_extract_addr(*addr);
if (*addr >= pool->addrs_cnt ||
*addr + pool->chunk_size > pool->addrs_cnt ||
xp_addr_crosses_non_contig_pg(pool, *addr))
return false;
return true;
}
static bool xp_check_aligned(struct xsk_buff_pool *pool, u64 *addr)
{
*addr = xp_aligned_extract_addr(pool, *addr);
return *addr < pool->addrs_cnt;
}
static struct xdp_buff_xsk *__xp_alloc(struct xsk_buff_pool *pool)
{
struct xdp_buff_xsk *xskb;
u64 addr;
bool ok;
if (pool->free_heads_cnt == 0)
return NULL;
xskb = pool->free_heads[--pool->free_heads_cnt];
for (;;) {
if (!xskq_cons_peek_addr_unchecked(pool->fq, &addr)) {
pool->fq->queue_empty_descs++;
xp_release(xskb);
return NULL;
}
ok = pool->unaligned ? xp_check_unaligned(pool, &addr) :
xp_check_aligned(pool, &addr);
if (!ok) {
pool->fq->invalid_descs++;
xskq_cons_release(pool->fq);
continue;
}
break;
}
xskq_cons_release(pool->fq);
xskb->orig_addr = addr;
xskb->xdp.data_hard_start = pool->addrs + addr + pool->headroom;
if (pool->dma_pages_cnt) {
xskb->frame_dma = (pool->dma_pages[addr >> PAGE_SHIFT] &
~XSK_NEXT_PG_CONTIG_MASK) +
(addr & ~PAGE_MASK);
xskb->dma = xskb->frame_dma + pool->headroom +
XDP_PACKET_HEADROOM;
}
return xskb;
}
struct xdp_buff *xp_alloc(struct xsk_buff_pool *pool)
{
struct xdp_buff_xsk *xskb;
if (!pool->free_list_cnt) {
xskb = __xp_alloc(pool);
if (!xskb)
return NULL;
} else {
pool->free_list_cnt--;
xskb = list_first_entry(&pool->free_list, struct xdp_buff_xsk,
free_list_node);
list_del(&xskb->free_list_node);
}
xskb->xdp.data = xskb->xdp.data_hard_start + XDP_PACKET_HEADROOM;
xskb->xdp.data_meta = xskb->xdp.data;
if (pool->dma_need_sync) {
dma_sync_single_range_for_device(pool->dev, xskb->dma, 0,
pool->frame_len,
DMA_BIDIRECTIONAL);
}
return &xskb->xdp;
}
EXPORT_SYMBOL(xp_alloc);
bool xp_can_alloc(struct xsk_buff_pool *pool, u32 count)
{
if (pool->free_list_cnt >= count)
return true;
return xskq_cons_has_entries(pool->fq, count - pool->free_list_cnt);
}
EXPORT_SYMBOL(xp_can_alloc);
void xp_free(struct xdp_buff_xsk *xskb)
{
xskb->pool->free_list_cnt++;
list_add(&xskb->free_list_node, &xskb->pool->free_list);
}
EXPORT_SYMBOL(xp_free);
void *xp_raw_get_data(struct xsk_buff_pool *pool, u64 addr)
{
addr = pool->unaligned ? xp_unaligned_add_offset_to_addr(addr) : addr;
return pool->addrs + addr;
}
EXPORT_SYMBOL(xp_raw_get_data);
dma_addr_t xp_raw_get_dma(struct xsk_buff_pool *pool, u64 addr)
{
addr = pool->unaligned ? xp_unaligned_add_offset_to_addr(addr) : addr;
return (pool->dma_pages[addr >> PAGE_SHIFT] &
~XSK_NEXT_PG_CONTIG_MASK) +
(addr & ~PAGE_MASK);
}
EXPORT_SYMBOL(xp_raw_get_dma);
void xp_dma_sync_for_cpu_slow(struct xdp_buff_xsk *xskb)
{
dma_sync_single_range_for_cpu(xskb->pool->dev, xskb->dma, 0,
xskb->pool->frame_len, DMA_BIDIRECTIONAL);
}
EXPORT_SYMBOL(xp_dma_sync_for_cpu_slow);
void xp_dma_sync_for_device_slow(struct xsk_buff_pool *pool, dma_addr_t dma,
size_t size)
{
dma_sync_single_range_for_device(pool->dev, dma, 0,
size, DMA_BIDIRECTIONAL);
}
EXPORT_SYMBOL(xp_dma_sync_for_device_slow);