* [PATCH net-next v3 1/4] net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding
2026-06-12 16:25 [PATCH net-next v3 0/4] net: devmem: allow rx-buf-size > PAGE_SIZE per binding Bobby Eshleman
@ 2026-06-12 16:25 ` Bobby Eshleman
2026-06-12 16:25 ` [PATCH net-next v3 2/4] udmabuf: emit one sg entry per pinned folio Bobby Eshleman
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Bobby Eshleman @ 2026-06-12 16:25 UTC (permalink / raw)
To: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan
Cc: netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
From: Bobby Eshleman <bobbyeshleman@meta.com>
Every devmem dmabuf binding today hands the page_pool PAGE_SIZE niovs.
This caps a single RX descriptor at PAGE_SIZE, burning CPU on buffer
churn for large flows.
Add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_BUF_SIZE, that
lets userspace request a larger niov size. The value must be a power of
two >= PAGE_SIZE.
Measurements
------------
Setup: kperf in devmem RX/TX cuda mode, 4 flows, 64 MB messages, 60s,
dctcp, num-rx-queues=4, dmabuf-rx/tx-size-mb=2048, 10 runs per niov
size, mlx5.
CPU Util:
niov net sirq % net idle % app sys % app idle %
----- ---------------- ---------------- ---------------- ----------------
4K 62.38 +/- 8.27 33.40 +/- 7.51 54.15 +/- 10.23 43.67 +/- 10.53
16K 58.91 +/- 5.35 35.23 +/- 5.88 41.05 +/- 8.87 56.42 +/- 9.24
32K 64.12 +/- 0.68 31.09 +/- 1.48 44.54 +/- 3.51 52.63 +/- 3.65
64K 54.69 +/- 5.54 39.67 +/- 5.81 35.47 +/- 3.11 61.97 +/- 3.27
RX app sys % drops ~19% from 4K to 64K.
Throughput:
niov RX dev Gbps RX flow avg Gbps
----- ---------------- -----------------
4K 300.63 +/- 53.21 75.16 +/- 13.30
16K 321.35 +/- 28.20 80.34 +/- 7.05
32K 347.63 +/- 2.20 86.91 +/- 0.55
64K 332.11 +/- 14.26 83.03 +/- 3.56
Throughput seems to increase, but the stdev is pretty wide so could just
be noise.
kperf support (not yet merged):
https://github.com/facebookexperimental/kperf/commit/8837577f920876bce6986ec18869ac04439ebcd2
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
---
Documentation/netlink/specs/netdev.yaml | 8 ++++++
include/uapi/linux/netdev.h | 1 +
net/core/devmem.c | 51 +++++++++++++++++++--------------
net/core/devmem.h | 13 ++++++---
net/core/netdev-genl-gen.c | 5 ++--
net/core/netdev-genl.c | 19 ++++++++++--
tools/include/uapi/linux/netdev.h | 1 +
7 files changed, 69 insertions(+), 29 deletions(-)
diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index 49862b666d7d..395eaa0f9580 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -591,6 +591,13 @@ attribute-sets:
type: u32
checks:
min: 1
+ -
+ name: rx-buf-size
+ doc: |
+ Size in bytes of each RX buffer the NIC writes into from the bound
+ dmabuf. Must be a power of two and >= PAGE_SIZE; defaults to
+ PAGE_SIZE.
+ type: u32
operations:
list:
@@ -805,6 +812,7 @@ operations:
- ifindex
- fd
- queues
+ - rx-buf-size
reply:
attributes:
- id
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 7df1056a35fd..180a4ffffd60 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -217,6 +217,7 @@ enum {
NETDEV_A_DMABUF_QUEUES,
NETDEV_A_DMABUF_FD,
NETDEV_A_DMABUF_ID,
+ NETDEV_A_DMABUF_RX_BUF_SIZE,
__NETDEV_A_DMABUF_MAX,
NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 957d6b96216b..3ce3cc14bec0 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -46,7 +46,7 @@ static dma_addr_t net_devmem_get_dma_addr(const struct net_iov *niov)
owner = net_devmem_iov_to_chunk_owner(niov);
return owner->base_dma_addr +
- ((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
+ ((dma_addr_t)net_iov_idx(niov) << owner->binding->niov_shift);
}
static void net_devmem_dmabuf_binding_release(struct percpu_ref *ref)
@@ -93,13 +93,14 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
ssize_t offset;
ssize_t index;
- dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE,
+ dma_addr = gen_pool_alloc_owner(binding->chunk_pool,
+ 1UL << binding->niov_shift,
(void **)&owner);
if (!dma_addr)
return NULL;
offset = dma_addr - owner->base_dma_addr;
- index = offset / PAGE_SIZE;
+ index = offset >> binding->niov_shift;
niov = &owner->area.niovs[index];
niov->desc.pp_magic = 0;
@@ -113,12 +114,13 @@ void net_devmem_free_dmabuf(struct net_iov *niov)
{
struct net_devmem_dmabuf_binding *binding = net_devmem_iov_binding(niov);
unsigned long dma_addr = net_devmem_get_dma_addr(niov);
+ size_t niov_size = 1UL << binding->niov_shift;
if (WARN_ON(!gen_pool_has_addr(binding->chunk_pool, dma_addr,
- PAGE_SIZE)))
+ niov_size)))
return;
- gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
+ gen_pool_free(binding->chunk_pool, dma_addr, niov_size);
}
void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
@@ -163,6 +165,9 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
u32 xa_idx;
int err;
+ if (binding->niov_shift != PAGE_SHIFT)
+ mp_params.rx_page_size = 1U << binding->niov_shift;
+
err = netif_mp_open_rxq(dev, rxq_idx, &mp_params, extack);
if (err)
return err;
@@ -184,14 +189,16 @@ struct net_devmem_dmabuf_binding *
net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
- unsigned int dmabuf_fd, struct netdev_nl_sock *priv,
+ unsigned int dmabuf_fd, unsigned int niov_shift,
+ struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack)
{
struct net_devmem_dmabuf_binding *binding;
+ size_t niov_size = 1UL << niov_shift;
static u32 id_alloc_next;
+ unsigned int sg_idx, i;
struct scatterlist *sg;
struct dma_buf *dmabuf;
- unsigned int sg_idx, i;
unsigned long virtual;
int err;
@@ -213,6 +220,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
binding->dev = dev;
binding->vdev = vdev;
+ binding->niov_shift = niov_shift;
xa_init_flags(&binding->bound_rxqs, XA_FLAGS_ALLOC);
err = percpu_ref_init(&binding->ref,
@@ -248,18 +256,14 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
goto err_unmap;
}
binding->tx_vec = kvmalloc_objs(struct net_iov *,
- dmabuf->size / PAGE_SIZE);
+ dmabuf->size >> niov_shift);
if (!binding->tx_vec) {
err = -ENOMEM;
goto err_unmap;
}
}
- /* For simplicity we expect to make PAGE_SIZE allocations, but the
- * binding can be much more flexible than that. We may be able to
- * allocate MTU sized chunks here. Leave that for future work...
- */
- binding->chunk_pool = gen_pool_create(PAGE_SHIFT,
+ binding->chunk_pool = gen_pool_create(niov_shift,
dev_to_node(&dev->dev));
if (!binding->chunk_pool) {
err = -ENOMEM;
@@ -273,9 +277,12 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
size_t len = sg_dma_len(sg);
struct net_iov *niov;
- if (!IS_ALIGNED(len, PAGE_SIZE)) {
+ if (!IS_ALIGNED(dma_addr, niov_size) ||
+ !IS_ALIGNED(len, niov_size)) {
err = -EINVAL;
- NL_SET_ERR_MSG(extack, "dma-buf SG length must be PAGE_SIZE aligned");
+ NL_SET_ERR_MSG_FMT(extack,
+ "dmabuf sg entry (addr=%pad, len=%zu) not aligned to niov size %zu",
+ &dma_addr, len, niov_size);
goto err_free_chunks;
}
@@ -288,7 +295,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
owner->area.base_virtual = virtual;
owner->base_dma_addr = dma_addr;
- owner->area.num_niovs = len / PAGE_SIZE;
+ owner->area.num_niovs = len >> niov_shift;
owner->binding = binding;
err = gen_pool_add_owner(binding->chunk_pool, dma_addr,
@@ -313,7 +320,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
net_devmem_get_dma_addr(niov));
if (direction == DMA_TO_DEVICE)
- binding->tx_vec[owner->area.base_virtual / PAGE_SIZE + i] = niov;
+ binding->tx_vec[(owner->area.base_virtual >> niov_shift) + i] = niov;
}
virtual += len;
@@ -430,13 +437,15 @@ struct net_iov *
net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding,
size_t virt_addr, size_t *off, size_t *size)
{
+ size_t niov_size = 1UL << binding->niov_shift;
+
if (virt_addr >= binding->dmabuf->size)
return NULL;
- *off = virt_addr % PAGE_SIZE;
- *size = PAGE_SIZE - *off;
+ *off = virt_addr & (niov_size - 1);
+ *size = niov_size - *off;
- return binding->tx_vec[virt_addr / PAGE_SIZE];
+ return binding->tx_vec[virt_addr >> binding->niov_shift];
}
/*** "Dmabuf devmem memory provider" ***/
@@ -454,7 +463,7 @@ int mp_dmabuf_devmem_init(struct page_pool *pool)
pool->dma_sync = false;
pool->dma_sync_for_cpu = false;
- if (pool->p.order != 0)
+ if (pool->p.order != binding->niov_shift - PAGE_SHIFT)
return -E2BIG;
net_devmem_dmabuf_binding_get(binding);
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 3852a56036cb..4a293a7d1149 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -71,6 +71,8 @@ struct net_devmem_dmabuf_binding {
*/
struct net_iov **tx_vec;
+ unsigned int niov_shift;
+
struct work_struct unbind_w;
};
@@ -93,7 +95,8 @@ struct net_devmem_dmabuf_binding *
net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
- unsigned int dmabuf_fd, struct netdev_nl_sock *priv,
+ unsigned int dmabuf_fd, unsigned int niov_shift,
+ struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack);
struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id);
void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
@@ -122,10 +125,11 @@ static inline u32 net_devmem_iov_binding_id(const struct net_iov *niov)
static inline unsigned long net_iov_virtual_addr(const struct net_iov *niov)
{
- struct net_iov_area *owner = net_iov_owner(niov);
+ struct dmabuf_genpool_chunk_owner *co =
+ net_devmem_iov_to_chunk_owner(niov);
- return owner->base_virtual +
- ((unsigned long)net_iov_idx(niov) << PAGE_SHIFT);
+ return net_iov_owner(niov)->base_virtual +
+ ((unsigned long)net_iov_idx(niov) << co->binding->niov_shift);
}
static inline bool
@@ -175,6 +179,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
struct device *dma_dev,
enum dma_data_direction direction,
unsigned int dmabuf_fd,
+ unsigned int niov_shift,
struct netdev_nl_sock *priv,
struct netlink_ext_ack *extack)
{
diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
index d18c89b5a6c7..447ed06d8c74 100644
--- a/net/core/netdev-genl-gen.c
+++ b/net/core/netdev-genl-gen.c
@@ -106,10 +106,11 @@ static const struct nla_policy netdev_qstats_get_nl_policy[NETDEV_A_QSTATS_SCOPE
};
/* NETDEV_CMD_BIND_RX - do */
-static const struct nla_policy netdev_bind_rx_nl_policy[NETDEV_A_DMABUF_FD + 1] = {
+static const struct nla_policy netdev_bind_rx_nl_policy[NETDEV_A_DMABUF_RX_BUF_SIZE + 1] = {
[NETDEV_A_DMABUF_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
[NETDEV_A_DMABUF_FD] = { .type = NLA_U32, },
[NETDEV_A_DMABUF_QUEUES] = NLA_POLICY_NESTED(netdev_queue_id_nl_policy),
+ [NETDEV_A_DMABUF_RX_BUF_SIZE] = { .type = NLA_U32, },
};
/* NETDEV_CMD_NAPI_SET - do */
@@ -219,7 +220,7 @@ static const struct genl_split_ops netdev_nl_ops[] = {
.cmd = NETDEV_CMD_BIND_RX,
.doit = netdev_nl_bind_rx_doit,
.policy = netdev_bind_rx_nl_policy,
- .maxattr = NETDEV_A_DMABUF_FD,
+ .maxattr = NETDEV_A_DMABUF_RX_BUF_SIZE,
.flags = GENL_UNS_ADMIN_PERM | GENL_CMD_CAP_DO,
},
{
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b4d48f3672a5..020876528314 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1011,6 +1011,7 @@ netdev_nl_get_dma_dev(struct net_device *netdev, unsigned long *rxq_bitmap,
int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
{
struct net_devmem_dmabuf_binding *binding;
+ unsigned int niov_shift = PAGE_SHIFT;
u32 ifindex, dmabuf_fd, rxq_idx;
struct netdev_nl_sock *priv;
struct net_device *netdev;
@@ -1028,6 +1029,19 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
ifindex = nla_get_u32(info->attrs[NETDEV_A_DEV_IFINDEX]);
dmabuf_fd = nla_get_u32(info->attrs[NETDEV_A_DMABUF_FD]);
+ if (info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]) {
+ u32 rx_buf_size = nla_get_u32(info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]);
+
+ if (!rx_buf_size || !is_power_of_2(rx_buf_size) ||
+ rx_buf_size < PAGE_SIZE) {
+ NL_SET_ERR_MSG_FMT(info->extack,
+ "rx_buf_size %u must be a power of 2 >= page size (%lu)",
+ rx_buf_size, PAGE_SIZE);
+ return -EINVAL;
+ }
+ niov_shift = ilog2(rx_buf_size);
+ }
+
priv = genl_sk_priv_get(&netdev_nl_family, NETLINK_CB(skb).sk);
if (IS_ERR(priv))
return PTR_ERR(priv);
@@ -1078,7 +1092,8 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
}
binding = net_devmem_bind_dmabuf(netdev, NULL, dma_dev, DMA_FROM_DEVICE,
- dmabuf_fd, priv, info->extack);
+ dmabuf_fd, niov_shift, priv,
+ info->extack);
if (IS_ERR(binding)) {
err = PTR_ERR(binding);
goto err_rxq_bitmap;
@@ -1221,7 +1236,7 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
binding = net_devmem_bind_dmabuf(bind_dev,
bind_dev != netdev ? netdev : NULL,
dma_dev, DMA_TO_DEVICE, dmabuf_fd,
- priv, info->extack);
+ PAGE_SHIFT, priv, info->extack);
if (IS_ERR(binding)) {
err = PTR_ERR(binding);
goto err_unlock_bind_dev;
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index 7df1056a35fd..180a4ffffd60 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -217,6 +217,7 @@ enum {
NETDEV_A_DMABUF_QUEUES,
NETDEV_A_DMABUF_FD,
NETDEV_A_DMABUF_ID,
+ NETDEV_A_DMABUF_RX_BUF_SIZE,
__NETDEV_A_DMABUF_MAX,
NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
--
2.53.0-Meta
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH net-next v3 2/4] udmabuf: emit one sg entry per pinned folio
2026-06-12 16:25 [PATCH net-next v3 0/4] net: devmem: allow rx-buf-size > PAGE_SIZE per binding Bobby Eshleman
2026-06-12 16:25 ` [PATCH net-next v3 1/4] net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding Bobby Eshleman
@ 2026-06-12 16:25 ` Bobby Eshleman
2026-06-12 16:25 ` [PATCH net-next v3 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind Bobby Eshleman
2026-06-12 16:26 ` [PATCH net-next v3 4/4] selftests/net: devmem.py: add check_rx_large_niov Bobby Eshleman
3 siblings, 0 replies; 7+ messages in thread
From: Bobby Eshleman @ 2026-06-12 16:25 UTC (permalink / raw)
To: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan
Cc: netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
From: Bobby Eshleman <bobbyeshleman@meta.com>
get_sg_table() emitted one PAGE_SIZE sg entry per page even when the
underlying folio was larger.
Instead, walk folios[] and emit one sg entry per folio. When folios
represent large pages (as is for MFD_HUGETLB), each sg entry is a large
page. Normal PAGE_SIZE sg tables are unchanged.
This is helpful for importers like net/core/devmem that expect dmabuf sg
entries to be size and length aligned. Prior to this patch udmabuf
handed over one PAGE_SIZE sg entry per page, so devmem only saw
PAGE_SIZE chunks regardless of the underlying folio size.
dma_map_sgtable() does not always merge contiguous pages for us, so we
do this internally before exporting.
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
drivers/dma-buf/udmabuf.c | 52 ++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 47 insertions(+), 5 deletions(-)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 94b8ecb892bb..9b751dd98b12 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -141,26 +141,68 @@ static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
vm_unmap_ram(map->vaddr, ubuf->pagecount);
}
+/* Return the number of contiguous pages backed by the folio at @i.
+ * A udmabuf may map only part of a folio, or reference the same folio
+ * in multiple non-contiguous runs, so folio_nr_pages() can't be used.
+ */
+static pgoff_t udmabuf_folio_nr_pages(struct udmabuf *ubuf, pgoff_t i)
+{
+ struct folio *f = ubuf->folios[i];
+ pgoff_t j;
+
+ for (j = 1; i + j < ubuf->pagecount; j++) {
+ if (ubuf->folios[i + j] != f)
+ break;
+ /* Same folio, but not a sequential offset within it. */
+ if (ubuf->offsets[i + j] != ubuf->offsets[i] + j * PAGE_SIZE)
+ break;
+ }
+ return j;
+}
+
+/* Count the contiguous folio runs in @ubuf, one sg entry per run.
+ *
+ * Coalescing folios into a single sg entry up front lets importers actually
+ * see large chunks. We can't rely on dma_map_sgtable() to do this for us as
+ * the dma_map_direct() path preserves the input scatterlist lengths verbatim.
+ */
+static unsigned int udmabuf_sg_nents(struct udmabuf *ubuf)
+{
+ unsigned int nents = 0;
+ pgoff_t i;
+
+ for (i = 0; i < ubuf->pagecount; i += udmabuf_folio_nr_pages(ubuf, i))
+ nents++;
+ return nents;
+}
+
static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
enum dma_data_direction direction)
{
struct udmabuf *ubuf = buf->priv;
- struct sg_table *sg;
struct scatterlist *sgl;
- unsigned int i = 0;
+ struct sg_table *sg;
+ pgoff_t i, run;
+ unsigned int nents;
int ret;
+ nents = udmabuf_sg_nents(ubuf);
+
sg = kzalloc_obj(*sg);
if (!sg)
return ERR_PTR(-ENOMEM);
- ret = sg_alloc_table(sg, ubuf->pagecount, GFP_KERNEL);
+ ret = sg_alloc_table(sg, nents, GFP_KERNEL);
if (ret < 0)
goto err_alloc;
- for_each_sg(sg->sgl, sgl, ubuf->pagecount, i)
- sg_set_folio(sgl, ubuf->folios[i], PAGE_SIZE,
+ sgl = sg->sgl;
+ for (i = 0; i < ubuf->pagecount; i += run) {
+ run = udmabuf_folio_nr_pages(ubuf, i);
+ sg_set_folio(sgl, ubuf->folios[i], run << PAGE_SHIFT,
ubuf->offsets[i]);
+ sgl = sg_next(sgl);
+ }
ret = dma_map_sgtable(dev, sg, direction, 0);
if (ret < 0)
--
2.53.0-Meta
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH net-next v3 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind
2026-06-12 16:25 [PATCH net-next v3 0/4] net: devmem: allow rx-buf-size > PAGE_SIZE per binding Bobby Eshleman
2026-06-12 16:25 ` [PATCH net-next v3 1/4] net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding Bobby Eshleman
2026-06-12 16:25 ` [PATCH net-next v3 2/4] udmabuf: emit one sg entry per pinned folio Bobby Eshleman
@ 2026-06-12 16:25 ` Bobby Eshleman
2026-06-13 2:03 ` Stanislav Fomichev
2026-06-12 16:26 ` [PATCH net-next v3 4/4] selftests/net: devmem.py: add check_rx_large_niov Bobby Eshleman
3 siblings, 1 reply; 7+ messages in thread
From: Bobby Eshleman @ 2026-06-12 16:25 UTC (permalink / raw)
To: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan
Cc: netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
From: Bobby Eshleman <bobbyeshleman@meta.com>
Add -b <bytes> to request a non-default niov size via
NETDEV_A_DMABUF_RX_BUF_SIZE. When the value exceeds PAGE_SIZE,
udmabuf_alloc() switches to an MFD_HUGETLB-backed memfd so each 2 MB
hugepage produces one naturally-aligned sg entry.
Reject values > 2 MB up front: MFD_HUGETLB + udmabuf can only guarantee
2 MB per sg entry (one hugepage), so a larger rx_buf_size would fail the
per-sg length/alignment check.
Add CONFIG_HUGETLBFS=y to drivers/net/hw/config so the new path is
reachable in the CI kernels built for these tests.
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
tools/testing/selftests/drivers/net/hw/config | 1 +
tools/testing/selftests/drivers/net/hw/ncdevmem.c | 36 +++++++++++++++++++++--
2 files changed, 34 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/drivers/net/hw/config b/tools/testing/selftests/drivers/net/hw/config
index cd20024218cd..ed8642b68094 100644
--- a/tools/testing/selftests/drivers/net/hw/config
+++ b/tools/testing/selftests/drivers/net/hw/config
@@ -3,6 +3,7 @@ CONFIG_FAIL_FUNCTION=y
CONFIG_FAULT_INJECTION=y
CONFIG_FAULT_INJECTION_DEBUG_FS=y
CONFIG_FUNCTION_ERROR_INJECTION=y
+CONFIG_HUGETLBFS=y
CONFIG_INET6_ESP=y
CONFIG_INET6_ESP_OFFLOAD=y
CONFIG_INET_ESP=y
diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
index d96e8a3b5a65..a16e55af51ee 100644
--- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c
+++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
@@ -40,6 +40,7 @@
#include <linux/uio.h>
#include <stdarg.h>
+#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
@@ -61,6 +62,7 @@
#include <sys/time.h>
#include <linux/memfd.h>
+#include <sys/param.h>
#include <linux/dma-buf.h>
#include <linux/errqueue.h>
#include <linux/udmabuf.h>
@@ -79,6 +81,7 @@
#define PAGE_SHIFT 12
#define TEST_PREFIX "ncdevmem"
#define NUM_PAGES 16000
+#define MB(x) ((x) << 20)
#ifndef MSG_SOCK_DEVMEM
#define MSG_SOCK_DEVMEM 0x2000000
@@ -100,6 +103,7 @@ static unsigned int dmabuf_id;
static uint32_t tx_dmabuf_id;
static int waittime_ms = 500;
static bool fail_on_linear;
+static uint32_t rx_buf_size;
/* System state loaded by current_config_load() */
#define MAX_FLOWS 8
@@ -142,6 +146,7 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
{
struct udmabuf_create create;
struct memory_buffer *ctx;
+ unsigned int memfd_flags;
int ret;
ctx = malloc(sizeof(*ctx));
@@ -156,9 +161,14 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
goto err_free_ctx;
}
- ctx->memfd = memfd_create("udmabuf-test", MFD_ALLOW_SEALING);
+ memfd_flags = MFD_ALLOW_SEALING;
+ if (rx_buf_size > getpagesize())
+ memfd_flags |= MFD_HUGETLB | MFD_HUGE_2MB;
+
+ ctx->memfd = memfd_create("udmabuf-test", memfd_flags);
if (ctx->memfd < 0) {
- pr_err("[skip,no-memfd]");
+ pr_err("[skip,no-memfd%s]",
+ (memfd_flags & MFD_HUGETLB) ? " (need hugepages)" : "");
goto err_close_dev;
}
@@ -168,6 +178,11 @@ static struct memory_buffer *udmabuf_alloc(size_t size)
goto err_close_memfd;
}
+ if (memfd_flags & MFD_HUGETLB) {
+ size = roundup(size, MB(2));
+ ctx->size = size;
+ }
+
ret = ftruncate(ctx->memfd, size);
if (ret == -1) {
pr_err("[FAIL,memfd-truncate]");
@@ -699,6 +714,8 @@ static int bind_rx_queue(unsigned int ifindex, unsigned int dmabuf_fd,
netdev_bind_rx_req_set_ifindex(req, ifindex);
netdev_bind_rx_req_set_fd(req, dmabuf_fd);
__netdev_bind_rx_req_set_queues(req, queues, n_queue_index);
+ if (rx_buf_size)
+ netdev_bind_rx_req_set_rx_buf_size(req, rx_buf_size);
rsp = netdev_bind_rx(*ys, req);
if (!rsp) {
@@ -1411,7 +1428,7 @@ int main(int argc, char *argv[])
int is_server = 0, opt;
int ret, err = 1;
- while ((opt = getopt(argc, argv, "Lls:c:p:v:q:t:f:z:n")) != -1) {
+ while ((opt = getopt(argc, argv, "Lls:c:p:v:q:t:f:z:nb:")) != -1) {
switch (opt) {
case 'L':
fail_on_linear = true;
@@ -1446,6 +1463,19 @@ int main(int argc, char *argv[])
case 'n':
skip_config = 1;
break;
+ case 'b': {
+ unsigned long val;
+
+ errno = 0;
+ val = strtoul(optarg, NULL, 0);
+ if ((val == ULONG_MAX && errno == ERANGE) ||
+ val > UINT32_MAX) {
+ pr_err("invalid rx_buf_size: %s", optarg);
+ return 1;
+ }
+ rx_buf_size = val;
+ break;
+ }
case '?':
fprintf(stderr, "unknown option: %c\n", optopt);
break;
--
2.53.0-Meta
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH net-next v3 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind
2026-06-12 16:25 ` [PATCH net-next v3 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind Bobby Eshleman
@ 2026-06-13 2:03 ` Stanislav Fomichev
0 siblings, 0 replies; 7+ messages in thread
From: Stanislav Fomichev @ 2026-06-13 2:03 UTC (permalink / raw)
To: Bobby Eshleman
Cc: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan,
netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
On 06/12, Bobby Eshleman wrote:
> From: Bobby Eshleman <bobbyeshleman@meta.com>
>
> Add -b <bytes> to request a non-default niov size via
> NETDEV_A_DMABUF_RX_BUF_SIZE. When the value exceeds PAGE_SIZE,
> udmabuf_alloc() switches to an MFD_HUGETLB-backed memfd so each 2 MB
> hugepage produces one naturally-aligned sg entry.
>
> Reject values > 2 MB up front: MFD_HUGETLB + udmabuf can only guarantee
> 2 MB per sg entry (one hugepage), so a larger rx_buf_size would fail the
> per-sg length/alignment check.
>
> Add CONFIG_HUGETLBFS=y to drivers/net/hw/config so the new path is
> reachable in the CI kernels built for these tests.
>
> Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH net-next v3 4/4] selftests/net: devmem.py: add check_rx_large_niov
2026-06-12 16:25 [PATCH net-next v3 0/4] net: devmem: allow rx-buf-size > PAGE_SIZE per binding Bobby Eshleman
` (2 preceding siblings ...)
2026-06-12 16:25 ` [PATCH net-next v3 3/4] selftests/net: ncdevmem: add -b option to set rx-buf-size on bind Bobby Eshleman
@ 2026-06-12 16:26 ` Bobby Eshleman
2026-06-13 2:03 ` Stanislav Fomichev
3 siblings, 1 reply; 7+ messages in thread
From: Bobby Eshleman @ 2026-06-12 16:26 UTC (permalink / raw)
To: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan
Cc: netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
From: Bobby Eshleman <bobbyeshleman@meta.com>
Add a new devmem test case for binding the dmabuf with rx-buf-size=16K.
The test sweeps RX payload sizes straddling the niov boundary to cover
the sub-niov, exact-niov, and multi-niov RX paths.
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
tools/testing/selftests/drivers/net/hw/devmem.py | 12 ++++-
.../testing/selftests/drivers/net/hw/devmem_lib.py | 58 +++++++++++++++++++++-
.../testing/selftests/drivers/net/hw/nk_devmem.py | 11 +++-
3 files changed, 75 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/drivers/net/hw/devmem.py b/tools/testing/selftests/drivers/net/hw/devmem.py
index 031cf9905f65..47b54e18e7a6 100755
--- a/tools/testing/selftests/drivers/net/hw/devmem.py
+++ b/tools/testing/selftests/drivers/net/hw/devmem.py
@@ -2,7 +2,8 @@
# SPDX-License-Identifier: GPL-2.0
from os import path
-from devmem_lib import setup_test, run_rx, run_tx, run_tx_chunks, run_rx_hds
+from devmem_lib import (setup_test, run_rx, run_tx, run_tx_chunks, run_rx_hds,
+ run_rx_large_niov)
from lib.py import ksft_run, ksft_exit, ksft_disruptive
from lib.py import NetDrvEpEnv
@@ -30,11 +31,18 @@ def check_rx_hds(cfg) -> None:
run_rx_hds(cfg)
+@ksft_disruptive
+def check_rx_large_niov(cfg) -> None:
+ """Run the devmem RX test with rx-buf-size = 16 KiB."""
+ run_rx_large_niov(cfg)
+
+
def main() -> None:
"""Run the devmem test cases."""
with NetDrvEpEnv(__file__) as cfg:
setup_test(cfg, path.abspath(path.dirname(__file__) + "/ncdevmem"))
- ksft_run([check_rx, check_tx, check_tx_chunks, check_rx_hds],
+ ksft_run([check_rx, check_tx, check_tx_chunks, check_rx_hds,
+ check_rx_large_niov],
args=(cfg,))
ksft_exit()
diff --git a/tools/testing/selftests/drivers/net/hw/devmem_lib.py b/tools/testing/selftests/drivers/net/hw/devmem_lib.py
index 0921ff03eb81..d2f00a876767 100644
--- a/tools/testing/selftests/drivers/net/hw/devmem_lib.py
+++ b/tools/testing/selftests/drivers/net/hw/devmem_lib.py
@@ -8,7 +8,7 @@ from lib.py import (bkg, cmd, defer, ethtool, rand_port, wait_port_listen,
NetdevFamily)
-def require_devmem(cfg):
+def require_devmem(cfg, rx_buf_size=0):
"""Probe ncdevmem on cfg.ifname and SKIP the test if devmem isn't supported."""
if not hasattr(cfg, "devmem_probed"):
probe_command = f"{cfg.bin_local} -f {cfg.ifname}"
@@ -18,6 +18,19 @@ def require_devmem(cfg):
if not cfg.devmem_supported:
raise KsftSkipEx("Test requires devmem support")
+ if rx_buf_size > 0:
+ if not hasattr(cfg, "devmem_rx_buf_size_probed"):
+ cfg.devmem_rx_buf_size_probed = {}
+
+ if rx_buf_size not in cfg.devmem_rx_buf_size_probed:
+ probe_command = f"{cfg.bin_local} -f {cfg.ifname} -b {rx_buf_size}"
+ cfg.devmem_rx_buf_size_probed[rx_buf_size] = \
+ cmd(probe_command, fail=False, shell=True).ret == 0
+
+ if not cfg.devmem_rx_buf_size_probed[rx_buf_size]:
+ raise KsftSkipEx(
+ f"Test requires devmem rx-buf-size={rx_buf_size} support")
+
def configure_nic(cfg):
"""Channels, rings, RSS, queue lease for netkit devmem."""
@@ -76,7 +89,8 @@ def set_flow_rule(cfg, port):
return int(re.search(r'ID (\d+)', output).group(1))
-def ncdevmem_rx(cfg, port, verify=True, fail_on_linear=False, flow_steer=False):
+def ncdevmem_rx(cfg, port, verify=True, fail_on_linear=False, flow_steer=False,
+ rx_buf_size=0):
"""Build the ncdevmem RX listener command."""
if hasattr(cfg, 'netns'):
flow_rule_id = set_flow_rule(cfg, port)
@@ -96,6 +110,8 @@ def ncdevmem_rx(cfg, port, verify=True, fail_on_linear=False, flow_steer=False):
extras.append("-v 7")
if fail_on_linear:
extras.append("-L")
+ if rx_buf_size > 0:
+ extras.append(f"-b {rx_buf_size}")
parts = [cfg.bin_local, "-l", f"-f {ifname}", f"-s {addr}",
f"-p {port}", *extras]
@@ -202,6 +218,44 @@ def run_tx_chunks(cfg):
ksft_eq(socat.stdout.strip(), "hello\nworld")
+def _restore_nr_hugepages(hp_file, nr_hugepages):
+ with open(hp_file, 'w', encoding='utf-8') as f:
+ f.write(str(nr_hugepages))
+
+
+def run_rx_large_niov(cfg):
+ """Run the devmem RX test with a large niov (rx-buf-size > PAGE_SIZE).
+
+ Sweep payload sizes that straddle the niov boundary: below, equal to,
+ and above rx_buf_size, to exercise sub-niov, exact-niov, and multi-niov
+ RX paths.
+ """
+ hp_file = "/proc/sys/vm/nr_hugepages"
+ with open(hp_file, 'r+', encoding='utf-8') as f:
+ nr_hugepages = int(f.read().strip())
+ if nr_hugepages < 64:
+ f.seek(0)
+ f.write("64")
+ defer(_restore_nr_hugepages, hp_file, nr_hugepages)
+ require_devmem(cfg, rx_buf_size=16384)
+ configure_nic(cfg)
+ netns = getattr(cfg, "netns", None)
+
+ for size in [1024, 4096, 8192, 16384, 32768, 65536]:
+ port = rand_port()
+ socat = socat_send(cfg, port)
+ listen_cmd = ncdevmem_rx(cfg, port,
+ flow_steer=not netns,
+ rx_buf_size=16384)
+ data_pipe = (f"yes $(echo -e \x01\x02\x03\x04\x05\x06) | "
+ f"head -c {size} | {socat}")
+ with bkg(listen_cmd, exit_wait=True, ns=netns) as ncdevmem:
+ wait_port_listen(port, proto="tcp", ns=netns)
+ cmd(data_pipe, host=cfg.remote, shell=True)
+ ksft_eq(ncdevmem.ret, 0,
+ f"large-niov failed for payload size {size}")
+
+
def run_rx_hds(cfg):
"""Run the HDS test by running devmem RX across a segment size sweep."""
require_devmem(cfg)
diff --git a/tools/testing/selftests/drivers/net/hw/nk_devmem.py b/tools/testing/selftests/drivers/net/hw/nk_devmem.py
index 300ed2a70ab4..7f1867e4ff32 100755
--- a/tools/testing/selftests/drivers/net/hw/nk_devmem.py
+++ b/tools/testing/selftests/drivers/net/hw/nk_devmem.py
@@ -3,7 +3,8 @@
"""Test devmem TCP with netkit."""
import os
-from devmem_lib import setup_test, run_rx, run_tx, run_tx_chunks, run_rx_hds
+from devmem_lib import (setup_test, run_rx, run_tx, run_tx_chunks, run_rx_hds,
+ run_rx_large_niov)
from lib.py import ksft_run, ksft_exit, ksft_disruptive
from lib.py import NetDrvContEnv
@@ -31,6 +32,12 @@ def check_nk_rx_hds(cfg) -> None:
run_rx_hds(cfg)
+@ksft_disruptive
+def check_nk_rx_large_niov(cfg) -> None:
+ """Run the devmem RX large-niov test through netkit."""
+ run_rx_large_niov(cfg)
+
+
def main() -> None:
"""Run the netkit devmem test cases."""
with NetDrvContEnv(__file__, rxqueues=2, primary_rx_redirect=True) as cfg:
@@ -38,7 +45,7 @@ def main() -> None:
os.path.join(os.path.dirname(os.path.abspath(__file__)),
"ncdevmem"))
ksft_run([check_nk_rx, check_nk_tx, check_nk_tx_chunks,
- check_nk_rx_hds], args=(cfg,))
+ check_nk_rx_hds, check_nk_rx_large_niov], args=(cfg,))
ksft_exit()
--
2.53.0-Meta
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH net-next v3 4/4] selftests/net: devmem.py: add check_rx_large_niov
2026-06-12 16:26 ` [PATCH net-next v3 4/4] selftests/net: devmem.py: add check_rx_large_niov Bobby Eshleman
@ 2026-06-13 2:03 ` Stanislav Fomichev
0 siblings, 0 replies; 7+ messages in thread
From: Stanislav Fomichev @ 2026-06-13 2:03 UTC (permalink / raw)
To: Bobby Eshleman
Cc: Donald Hunter, Jakub Kicinski, David S. Miller, Eric Dumazet,
Paolo Abeni, Simon Horman, Andrew Lunn, Gerd Hoffmann,
Vivek Kasireddy, Sumit Semwal, Christian König, Shuah Khan,
netdev, linux-kernel, dri-devel, linux-media, linaro-mm-sig,
linux-kselftest, sdf, razor, daniel, almasrymina, matttbe,
skhawaja, dw, Bobby Eshleman
On 06/12, Bobby Eshleman wrote:
> From: Bobby Eshleman <bobbyeshleman@meta.com>
>
> Add a new devmem test case for binding the dmabuf with rx-buf-size=16K.
> The test sweeps RX payload sizes straddling the niov boundary to cover
> the sub-niov, exact-niov, and multi-niov RX paths.
>
> Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
^ permalink raw reply [flat|nested] 7+ messages in thread