On Sun, Jul 19, 2026 at 11:03 AM Taehee Yoo <[email protected]> wrote: > > Extend the devmem memory-provider path so a knod accelerator can back a > NIC page_pool with accelerator-exported memory (dma-buf), letting the > NIC DMA received packets directly into accelerator memory. > > Signed-off-by: Taehee Yoo <[email protected]>
Changes look fine in general but I do not understand in the design how the page_pool not bound to rx queue would be used. Maybe elaborate on the design in the commit message or cover letter in the next iteration. > (cherry picked from commit d511a8cb3e229f8f5cf060985880d45bd384db87) I guess remove unintended cherry-pick tag. > --- > include/net/devmem.h | 58 +++++++++++++ > include/net/netmem.h | 9 +++ > include/net/page_pool/memory_provider.h | 4 + > include/net/page_pool/types.h | 23 +++++- > net/core/devmem.c | 103 +++++++++++++++++++----- > net/core/devmem.h | 7 +- > net/core/page_pool.c | 22 ++++- > 7 files changed, 198 insertions(+), 28 deletions(-) > create mode 100644 include/net/devmem.h > > diff --git a/include/net/devmem.h b/include/net/devmem.h > new file mode 100644 > index 000000000000..f1c3895d7833 > --- /dev/null > +++ b/include/net/devmem.h Try to keep only include/net/netmem.h and net/core/devmem.h rather than add an include/net/devmem.h > @@ -0,0 +1,58 @@ > +/* SPDX-License-Identifier: GPL-2.0-or-later */ > +/* > + * Device memory TCP support > + * > + * Authors: Mina Almasry <[email protected]> > + * Willem de Bruijn <[email protected]> > + * Kaiyuan Zhang <[email protected]> > + * > + */ > +#ifndef _NET_DEVMEM_H > +#define _NET_DEVMEM_H > + > +#include <linux/dma-direction.h> > +#include <linux/err.h> > +#include <linux/types.h> > + > +struct device; > +struct dma_buf; > +struct dma_buf_attach_ops; > +struct net_device; > +struct net_devmem_dmabuf_binding; > +struct netlink_ext_ack; > + > +#if defined(CONFIG_NET_DEVMEM) > +struct net_devmem_dmabuf_binding * > +__net_devmem_binding_create(struct net_device *dev, struct device *dma_dev, > + struct dma_buf *dmabuf, > + enum dma_data_direction direction, > + const struct dma_buf_attach_ops *importer_ops, > + struct netlink_ext_ack *extack); > +int net_devmem_bind_dmabuf_to_queue_direct(struct net_device *dev, u32 > rxq_idx, > + struct net_devmem_dmabuf_binding > *binding); > +void net_devmem_unbind_dmabuf_direct(struct net_devmem_dmabuf_binding > *binding); > +#else > +static inline struct net_devmem_dmabuf_binding * > +__net_devmem_binding_create(struct net_device *dev, struct device *dma_dev, > + struct dma_buf *dmabuf, > + enum dma_data_direction direction, > + const struct dma_buf_attach_ops *importer_ops, > + struct netlink_ext_ack *extack) > +{ > + return ERR_PTR(-EOPNOTSUPP); > +} > + > +static inline int > +net_devmem_bind_dmabuf_to_queue_direct(struct net_device *dev, u32 rxq_idx, > + struct net_devmem_dmabuf_binding > *binding) > +{ > + return -EOPNOTSUPP; > +} > + > +static inline void > +net_devmem_unbind_dmabuf_direct(struct net_devmem_dmabuf_binding *binding) > +{ > +} > +#endif > + > +#endif /* _NET_DEVMEM_H */ > diff --git a/include/net/netmem.h b/include/net/netmem.h > index bccacd21b6c3..3ddfbd37500f 100644 > --- a/include/net/netmem.h > +++ b/include/net/netmem.h > @@ -127,6 +127,15 @@ static inline void net_iov_init(struct net_iov *niov, > niov->type = type; > } > > +/* Global page index within the dma-buf, accounting for multi-chunk > + * scatter-gather layouts where each chunk owner's niovs start at 0. > + */ > +static inline unsigned int net_iov_binding_idx(const struct net_iov *niov) > +{ > + return (net_iov_owner(niov)->base_virtual >> PAGE_SHIFT) + > + net_iov_idx(niov); > +} > + > /* netmem */ > > /** > diff --git a/include/net/page_pool/memory_provider.h > b/include/net/page_pool/memory_provider.h > index 255ce4cfd975..4b58a9702fb7 100644 > --- a/include/net/page_pool/memory_provider.h > +++ b/include/net/page_pool/memory_provider.h > @@ -23,6 +23,10 @@ bool net_mp_niov_set_dma_addr(struct net_iov *niov, > dma_addr_t addr); > void net_mp_niov_set_page_pool(struct page_pool *pool, struct net_iov *niov); > void net_mp_niov_clear_page_pool(struct net_iov *niov); > > +void page_pool_provider_set_netmem(struct page_pool *pool, netmem_ref netmem, > + dma_addr_t addr); > +void page_pool_clear_pp_info(netmem_ref netmem); > + > int netif_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx, > const struct pp_memory_provider_params *p, > struct netlink_ext_ack *extack); > diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h > index 03da138722f5..3e866f249768 100644 > --- a/include/net/page_pool/types.h > +++ b/include/net/page_pool/types.h > @@ -31,8 +31,16 @@ > */ > #define PP_FLAG_ALLOW_UNREADABLE_NETMEM BIT(3) > > +/* Driver-managed pool with a directly-supplied memory provider, not bound > to a > + * netdev rx queue. Setting this flag requires page_pool_params.mp_ops and > + * .mp_priv to both be set. > + */ > +#define PP_FLAG_CUSTOM_MEMORY_PROVIDER BIT(4) > + > #define PP_FLAG_ALL (PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | \ > - PP_FLAG_SYSTEM_POOL | > PP_FLAG_ALLOW_UNREADABLE_NETMEM) > + PP_FLAG_SYSTEM_POOL | \ > + PP_FLAG_ALLOW_UNREADABLE_NETMEM | \ > + PP_FLAG_CUSTOM_MEMORY_PROVIDER) > > /* Index limit to stay within PP_DMA_INDEX_BITS for DMA indices */ > #define PP_DMA_INDEX_LIMIT XA_LIMIT(1, BIT(PP_DMA_INDEX_BITS) - 1) > @@ -54,11 +62,11 @@ > * would have to take a slower code path. > */ > #if PAGE_SIZE >= SZ_64K > -#define PP_ALLOC_CACHE_REFILL 4 > +#define PP_ALLOC_CACHE_REFILL 256 > #elif PAGE_SIZE >= SZ_16K > -#define PP_ALLOC_CACHE_REFILL 16 > +#define PP_ALLOC_CACHE_REFILL 1024 > #else > -#define PP_ALLOC_CACHE_REFILL 64 > +#define PP_ALLOC_CACHE_REFILL 4096 > #endif > I'm guessing this is just a workaround/optimization. You need a proper change for this, maybe make it configurable arguments when creating a pp or something. > #define PP_ALLOC_CACHE_SIZE (PP_ALLOC_CACHE_REFILL * 2) > @@ -67,6 +75,8 @@ struct pp_alloc_cache { > netmem_ref cache[PP_ALLOC_CACHE_SIZE]; > }; > > +struct memory_provider_ops; > + > /** > * struct page_pool_params - page pool parameters > * @fast: params accessed frequently on hotpath > @@ -83,6 +93,9 @@ struct pp_alloc_cache { > * @queue_idx: queue idx this page_pool is being created for. > * @flags: PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL, > * PP_FLAG_ALLOW_UNREADABLE_NETMEM. > + * @mp_ops: driver-supplied memory provider for a pool not bound to a > + * netdev rx queue (NULL to use rxq->mp_params instead) > + * @mp_priv: context passed to @mp_ops > */ > struct page_pool_params { > struct_group_tagged(page_pool_params_fast, fast, > @@ -99,6 +112,8 @@ struct page_pool_params { > struct net_device *netdev; > unsigned int queue_idx; > unsigned int flags; > + const struct memory_provider_ops *mp_ops; > + void *mp_priv; > /* private: used by test code only */ > void (*init_callback)(netmem_ref netmem, void *arg); > void *init_arg; > diff --git a/net/core/devmem.c b/net/core/devmem.c > index 957d6b96216b..9e21cffc9643 100644 > --- a/net/core/devmem.c > +++ b/net/core/devmem.c > @@ -121,12 +121,9 @@ void net_devmem_free_dmabuf(struct net_iov *niov) > gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE); > } > > -void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding) > +static void > +net_devmem_binding_unpublish(struct net_devmem_dmabuf_binding *binding) > { > - struct netdev_rx_queue *rxq; > - unsigned long xa_idx; > - unsigned int rxq_idx; > - > xa_erase(&net_devmem_dmabuf_bindings, binding->id); > > /* Ensure no tx net_devmem_lookup_dmabuf() are in flight after the > @@ -136,6 +133,15 @@ void net_devmem_unbind_dmabuf(struct > net_devmem_dmabuf_binding *binding) > > if (binding->list.next) > list_del(&binding->list); > +} > + > +void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding) > +{ > + struct netdev_rx_queue *rxq; > + unsigned long xa_idx; > + unsigned int rxq_idx; > + > + net_devmem_binding_unpublish(binding); > > xa_for_each(&binding->bound_rxqs, xa_idx, rxq) { > const struct pp_memory_provider_params mp_params = { > @@ -151,6 +157,47 @@ void net_devmem_unbind_dmabuf(struct > net_devmem_dmabuf_binding *binding) > percpu_ref_kill(&binding->ref); > } > > +/* Bind/unbind variants for in-kernel offload importers that drive the rx > + * queue lifecycle themselves. The mp_params are poked directly, without the > + * tcp-data-split/XDP guards or the queue reconfigure that the netlink > control > + * plane applies through netif_mp_open_rxq()/netif_mp_close_rxq(). > + */ > +int net_devmem_bind_dmabuf_to_queue_direct(struct net_device *dev, u32 > rxq_idx, > + struct net_devmem_dmabuf_binding > *binding) > +{ The LLM says in this function you need to check if the queue is already bound to a devmem tcp memory provider. -- Thanks, Mina
