Re: [PATCH net-next v24 06/13] memory-provider: dmabuf devmem memory provider

On Sat, 31 Aug 2024 00:43:06 +0000 Mina Almasry wrote:

diff --git a/include/net/mp_dmabuf_devmem.h b/include/net/mp_dmabuf_devmem.h new file mode 100644 index 000000000000..6d1cf2a77f6b --- /dev/null +++ b/include/net/mp_dmabuf_devmem.h

this header can live under net/core/ like netmem_priv.h right? devmem internals should be of no interest outside of core networking.

In fact the same is true for include/net/devmem.h ?

Sorry for pushing back on all the header exports, we have had bad experiences with people treating anything under include/ as public API for any subsystem to use..

@@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/*

• • Dmabuf device memory provider.
• • Authors: Mina Almasry almasrymina@google.com
• */

+#ifndef _NET_MP_DMABUF_DEVMEM_H +#define _NET_MP_DMABUF_DEVMEM_H

+#include <net/netmem.h>

+#if defined(CONFIG_NET_DEVMEM) +int mp_dmabuf_devmem_init(struct page_pool *pool);

+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp);

+void mp_dmabuf_devmem_destroy(struct page_pool *pool);

+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem); +#else +static inline int mp_dmabuf_devmem_init(struct page_pool *pool) +{

• return -EOPNOTSUPP;

+}

+static inline netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool,

• 					gfp_t gfp)
  

Please break the lines after the return type if the line gets long:

static inline netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp)

Please fix where you can (at least where it cases going over 80 chars)

+{

• return 0;

+}

+static inline void mp_dmabuf_devmem_destroy(struct page_pool *pool) +{ +}

+static inline bool mp_dmabuf_devmem_release_page(struct page_pool *pool,

• 				 netmem_ref netmem)
  

+{

• return false;

+} +#endif

+#endif /* _NET_MP_DMABUF_DEVMEM_H */ diff --git a/include/net/netmem.h b/include/net/netmem.h index ac6c7945117b..61400d4b0d66 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -8,6 +8,7 @@ #ifndef _NET_NETMEM_H #define _NET_NETMEM_H +#include <linux/mm.h> #include <net/devmem.h> #include <net/net_debug.h> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h index 4afd6dd56351..1b4698710f25 100644 --- a/include/net/page_pool/types.h +++ b/include/net/page_pool/types.h @@ -20,8 +20,17 @@ * device driver responsibility */ #define PP_FLAG_SYSTEM_POOL BIT(2) /* Global system page_pool */ +#define PP_FLAG_ALLOW_UNREADABLE_NETMEM BIT(3) /* Allow unreadable (net_iov

• 				* backed) netmem in this
  

• 				* page_pool. Drivers setting
  

• 				* this must be able to support
  

• 				* unreadable netmem, where
  

• 				* netmem_address() would return
  

• 				* NULL. This flag should not be
  

• 				* set for header page_pools.
  

• 				*/
  

Maybe move the comment before the define:

/* Allow unreadable (net_iov backed) netmem in this page_pool. Drivers setting * this must be able to support unreadable netmem, where netmem_address() would * return NULL. This flag should not be set for header page_pools. */ #define PP_FLAG_ALLOW_UNREADABLE_NETMEM BIT(3)

? up to you.

#define PP_FLAG_ALL (PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | \

• 		 PP_FLAG_SYSTEM_POOL)
  

• 		 PP_FLAG_SYSTEM_POOL | PP_FLAG_ALLOW_UNREADABLE_NETMEM)
  

/*

• Fast allocation side cache array/stack

@@ -57,7 +66,9 @@ struct pp_alloc_cache {

• @offset: DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
• @slow: params with slowpath access only (initialization and Netlink)
• @netdev: netdev this pool will serve (leave as NULL if none or multiple)

• • @flags: PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL

• • @queue: struct netdev_rx_queue 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.
    

  */

struct page_pool_params { struct_group_tagged(page_pool_params_fast, fast, @@ -72,6 +83,7 @@ struct page_pool_params { ); struct_group_tagged(page_pool_params_slow, slow, struct net_device *netdev;

• struct netdev_rx_queue *queue;
  

Why set a pointer? It should work but drivers don't usually deal with netdev_rx_queue struct directly. struct xdp_rxq_info takes an integer queue id, and it serves a somewhat similar function.

Keep in mind that there will be more drivers than core code, so convenience for them matters more.

unsigned int	flags;

/* private: used by test code only */ void (*init_callback)(netmem_ref netmem, void *arg); diff --git a/net/core/devmem.c b/net/core/devmem.c index 727e5ee39f30..c8c112360caa 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -13,6 +13,7 @@ #include <linux/netdevice.h> #include <linux/types.h> #include <net/devmem.h> +#include <net/mp_dmabuf_devmem.h> #include <net/netdev_queues.h> #include <net/netdev_rx_queue.h> #include <net/page_pool/helpers.h> @@ -320,3 +321,68 @@ void dev_dmabuf_uninstall(struct net_device *dev) } } }

+/*** "Dmabuf devmem memory provider" ***/

+int mp_dmabuf_devmem_init(struct page_pool *pool) +{

• struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
• if (!binding)

• return -EINVAL;
  

• if (!pool->dma_map)

• return -EOPNOTSUPP;
  

• if (pool->dma_sync)

• return -EOPNOTSUPP;
  

• if (pool->p.order != 0)

• return -E2BIG;
  

• net_devmem_dmabuf_binding_get(binding);
• return 0;

+}

+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp) +{

• struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
• netmem_ref netmem;
• struct net_iov *niov;

nit: reverse xmas tree

• niov = net_devmem_alloc_dmabuf(binding);
• if (!niov)

• return 0;
  

• netmem = net_iov_to_netmem(niov);
• page_pool_set_pp_info(pool, netmem);
• pool->pages_state_hold_cnt++;
• trace_page_pool_state_hold(pool, netmem, pool->pages_state_hold_cnt);
• return netmem;

+}

+void mp_dmabuf_devmem_destroy(struct page_pool *pool) +{

• struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
• net_devmem_dmabuf_binding_put(binding);

+}

+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem) +{

• if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))

• return false;
  

• if (WARN_ON_ONCE(atomic_long_read(netmem_get_pp_ref_count_ref(netmem)) !=

•      1))
  

something needs factoring out here, to make this line shorter, please.. either netmem -> net_iov conversion or at least reading of the ref count?

• return false;
  

• page_pool_clear_pp_info(netmem);
• net_devmem_free_dmabuf(netmem_to_net_iov(netmem));
• /* We don't want the page pool put_page()ing our net_iovs. */
• return false;

+} diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c index da11720a5983..e217a5838c87 100644 --- a/net/core/netdev_rx_queue.c +++ b/net/core/netdev_rx_queue.c @@ -4,8 +4,11 @@ #include <net/netdev_queues.h> #include <net/netdev_rx_queue.h> +#include "page_pool_priv.h"

int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx) {

• struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx); void *new_mem, *old_mem; int err;

@@ -31,6 +34,10 @@ int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx) if (err) goto err_free_old_mem;

• err = page_pool_check_memory_provider(dev, rxq);
• if (err)

• goto err_free_new_queue_mem;
  

• err = dev->queue_mgmt_ops->ndo_queue_stop(dev, old_mem, rxq_idx); if (err) goto err_free_new_queue_mem;

diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 52659db2d765..6e24950f2be4 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -11,6 +11,8 @@ #include <linux/slab.h> #include <linux/device.h> +#include <net/mp_dmabuf_devmem.h> +#include <net/netdev_rx_queue.h> #include <net/page_pool/helpers.h> #include <net/xdp.h> @@ -190,6 +192,7 @@ static int page_pool_init(struct page_pool *pool, int cpuid) { unsigned int ring_qsize = 1024; /* Default */

• int err;

page_pool_struct_check(); @@ -271,7 +274,36 @@ static int page_pool_init(struct page_pool *pool, if (pool->dma_map) get_device(pool->p.dev);

• if (pool->slow.queue &&

•    pool->slow.flags & PP_FLAG_ALLOW_UNREADABLE_NETMEM) {
  

• /* We rely on rtnl_lock()ing to make sure netdev_rx_queue
  

•  * configuration doesn't change while we're initializing the
  

nit: 'the' to next line

•  * page_pool.
  

•  */
  

• ASSERT_RTNL();
  

• pool->mp_priv = pool->slow.queue->mp_params.mp_priv;
  

• }