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page_pool: devmem support

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Convert netmem to be a union of struct page and struct netmem. Overload
the LSB of struct netmem* to indicate that it's a net_iov, otherwise
it's a page.

Currently these entries in struct page are rented by the page_pool and
used exclusively by the net stack:

struct {
	unsigned long pp_magic;
	struct page_pool *pp;
	unsigned long _pp_mapping_pad;
	unsigned long dma_addr;
	atomic_long_t pp_ref_count;
};

Mirror these (and only these) entries into struct net_iov and implement
netmem helpers that can access these common fields regardless of
whether the underlying type is page or net_iov.

Implement checks for net_iov in netmem helpers which delegate to mm
APIs, to ensure net_iov are never passed to the mm stack.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20240910171458.219195-6-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Mina Almasry 2024-09-10 17:14:49 +00:00 committed by Jakub Kicinski
parent 28c5c74eea
commit 8ab79ed50c
8 changed files with 218 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

124
include/net/netmem.h
View File

@ -8,12 +8,52 @@
#ifndef _NET_NETMEM_H
#define _NET_NETMEM_H
#include <linux/mm.h>
#include <net/net_debug.h>
/* net_iov */
DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
/* We overload the LSB of the struct page pointer to indicate whether it's
* a page or net_iov.
*/
#define NET_IOV 0x01UL
struct net_iov {
unsigned long __unused_padding;
unsigned long pp_magic;
struct page_pool *pp;
struct dmabuf_genpool_chunk_owner *owner;
unsigned long dma_addr;
atomic_long_t pp_ref_count;
};
/* These fields in struct page are used by the page_pool and net stack:
*
* struct {
* unsigned long pp_magic;
* struct page_pool *pp;
* unsigned long _pp_mapping_pad;
* unsigned long dma_addr;
* atomic_long_t pp_ref_count;
* };
*
* We mirror the page_pool fields here so the page_pool can access these fields
* without worrying whether the underlying fields belong to a page or net_iov.
*
* The non-net stack fields of struct page are private to the mm stack and must
* never be mirrored to net_iov.
*/
#define NET_IOV_ASSERT_OFFSET(pg, iov) \
static_assert(offsetof(struct page, pg) == \
offsetof(struct net_iov, iov))
NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);
NET_IOV_ASSERT_OFFSET(pp, pp);
NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);
NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
#undef NET_IOV_ASSERT_OFFSET
/* netmem */
/**
@ -27,20 +67,37 @@ struct net_iov {
*/
typedef unsigned long __bitwise netmem_ref;
static inline bool netmem_is_net_iov(const netmem_ref netmem)
{
return (__force unsigned long)netmem & NET_IOV;
}
/* This conversion fails (returns NULL) if the netmem_ref is not struct page
* backed.
*
* Currently struct page is the only possible netmem, and this helper never
* fails.
*/
static inline struct page *netmem_to_page(netmem_ref netmem)
{
if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
return NULL;
return (__force struct page *)netmem;
}
/* Converting from page to netmem is always safe, because a page can always be
* a netmem.
*/
static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
{
if (netmem_is_net_iov(netmem))
return (struct net_iov *)((__force unsigned long)netmem &
~NET_IOV);
DEBUG_NET_WARN_ON_ONCE(true);
return NULL;
}
static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
{
return (__force netmem_ref)((unsigned long)niov | NET_IOV);
}
static inline netmem_ref page_to_netmem(struct page *page)
{
return (__force netmem_ref)page;
@ -48,17 +105,70 @@ static inline netmem_ref page_to_netmem(struct page *page)
static inline int netmem_ref_count(netmem_ref netmem)
{
/* The non-pp refcount of net_iov is always 1. On net_iov, we only
* support pp refcounting which uses the pp_ref_count field.
*/
if (netmem_is_net_iov(netmem))
return 1;
return page_ref_count(netmem_to_page(netmem));
}
static inline unsigned long netmem_to_pfn(netmem_ref netmem)
static inline unsigned long netmem_pfn_trace(netmem_ref netmem)
{
if (netmem_is_net_iov(netmem))
return 0;
return page_to_pfn(netmem_to_page(netmem));
}
static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
{
return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);
}
static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
{
return __netmem_clear_lsb(netmem)->pp;
}
static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
{
return &__netmem_clear_lsb(netmem)->pp_ref_count;
}
static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
{
/* NUMA node preference only makes sense if we're allocating
* system memory. Memory providers (which give us net_iovs)
* choose for us.
*/
if (netmem_is_net_iov(netmem))
return true;
return page_to_nid(netmem_to_page(netmem)) == pref_nid;
}
static inline netmem_ref netmem_compound_head(netmem_ref netmem)
{
/* niov are never compounded */
if (netmem_is_net_iov(netmem))
return netmem;
return page_to_netmem(compound_head(netmem_to_page(netmem)));
}
static inline void *netmem_address(netmem_ref netmem)
{
if (netmem_is_net_iov(netmem))
return NULL;
return page_address(netmem_to_page(netmem));
}
static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
{
return __netmem_clear_lsb(netmem)->dma_addr;
}
#endif /* _NET_NETMEM_H */

39
include/net/page_pool/helpers.h
View File

@ -216,7 +216,7 @@ page_pool_get_dma_dir(const struct page_pool *pool)
static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
{
atomic_long_set(&netmem_to_page(netmem)->pp_ref_count, nr);
atomic_long_set(netmem_get_pp_ref_count_ref(netmem), nr);
}
/**
@ -244,7 +244,7 @@ static inline void page_pool_fragment_page(struct page *page, long nr)
static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
{
struct page *page = netmem_to_page(netmem);
atomic_long_t *pp_ref_count = netmem_get_pp_ref_count_ref(netmem);
long ret;
/* If nr == pp_ref_count then we have cleared all remaining
@ -261,19 +261,19 @@ static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
* initially, and only overwrite it when the page is partitioned into
* more than one piece.
*/
if (atomic_long_read(&page->pp_ref_count) == nr) {
if (atomic_long_read(pp_ref_count) == nr) {
/* As we have ensured nr is always one for constant case using
* the BUILD_BUG_ON(), only need to handle the non-constant case
* here for pp_ref_count draining, which is a rare case.
*/
BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
if (!__builtin_constant_p(nr))
atomic_long_set(&page->pp_ref_count, 1);
atomic_long_set(pp_ref_count, 1);
return 0;
}
ret = atomic_long_sub_return(nr, &page->pp_ref_count);
ret = atomic_long_sub_return(nr, pp_ref_count);
WARN_ON(ret < 0);
/* We are the last user here too, reset pp_ref_count back to 1 to
@ -282,7 +282,7 @@ static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
* page_pool_unref_page() currently.
*/
if (unlikely(!ret))
atomic_long_set(&page->pp_ref_count, 1);
atomic_long_set(pp_ref_count, 1);
return ret;
}
@ -401,9 +401,7 @@ static inline void page_pool_free_va(struct page_pool *pool, void *va,
static inline dma_addr_t page_pool_get_dma_addr_netmem(netmem_ref netmem)
{
struct page *page = netmem_to_page(netmem);
dma_addr_t ret = page->dma_addr;
dma_addr_t ret = netmem_get_dma_addr(netmem);
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
ret <<= PAGE_SHIFT;
@ -423,24 +421,6 @@ static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
return page_pool_get_dma_addr_netmem(page_to_netmem((struct page *)page));
}
static inline bool page_pool_set_dma_addr_netmem(netmem_ref netmem,
dma_addr_t addr)
{
struct page *page = netmem_to_page(netmem);
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
page->dma_addr = addr >> PAGE_SHIFT;
/* We assume page alignment to shave off bottom bits,
* if this "compression" doesn't work we need to drop.
*/
return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
}
page->dma_addr = addr;
return false;
}
/**
* page_pool_dma_sync_for_cpu - sync Rx page for CPU after it's written by HW
* @pool: &page_pool the @page belongs to
@ -463,11 +443,6 @@ static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
page_pool_get_dma_dir(pool));
}
static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
}
static inline bool page_pool_put(struct page_pool *pool)
{
return refcount_dec_and_test(&pool->user_cnt);

12
include/trace/events/page_pool.h
View File

@ -57,12 +57,12 @@ TRACE_EVENT(page_pool_state_release,
__entry->pool = pool;
__entry->netmem = (__force unsigned long)netmem;
__entry->release = release;
__entry->pfn = netmem_to_pfn(netmem);
__entry->pfn = netmem_pfn_trace(netmem);
),
TP_printk("page_pool=%p netmem=%p pfn=0x%lx release=%u",
TP_printk("page_pool=%p netmem=%p is_net_iov=%lu pfn=0x%lx release=%u",
__entry->pool, (void *)__entry->netmem,
__entry->pfn, __entry->release)
__entry->netmem & NET_IOV, __entry->pfn, __entry->release)
);
TRACE_EVENT(page_pool_state_hold,
@ -83,12 +83,12 @@ TRACE_EVENT(page_pool_state_hold,
__entry->pool = pool;
__entry->netmem = (__force unsigned long)netmem;
__entry->hold = hold;
__entry->pfn = netmem_to_pfn(netmem);
__entry->pfn = netmem_pfn_trace(netmem);
),
TP_printk("page_pool=%p netmem=%p pfn=0x%lx hold=%u",
TP_printk("page_pool=%p netmem=%p is_net_iov=%lu, pfn=0x%lx hold=%u",
__entry->pool, (void *)__entry->netmem,
__entry->pfn, __entry->hold)
__entry->netmem & NET_IOV, __entry->pfn, __entry->hold)
);
TRACE_EVENT(page_pool_update_nid,

7
net/core/devmem.c
View File

@ -18,6 +18,7 @@
#include <trace/events/page_pool.h>
#include "devmem.h"
#include "page_pool_priv.h"
/* Device memory support */
@ -82,6 +83,10 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
index = offset / PAGE_SIZE;
niov = &owner->niovs[index];
niov->pp_magic = 0;
niov->pp = NULL;
atomic_long_set(&niov->pp_ref_count, 0);
return niov;
}
@ -269,6 +274,8 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
for (i = 0; i < owner->num_niovs; i++) {
niov = &owner->niovs[i];
niov->owner = owner;
page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
net_devmem_get_dma_addr(niov));
}
virtual += len;

31
net/core/netmem_priv.h Normal file
View File

@ -0,0 +1,31 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NETMEM_PRIV_H
#define __NETMEM_PRIV_H
static inline unsigned long netmem_get_pp_magic(netmem_ref netmem)
{
return __netmem_clear_lsb(netmem)->pp_magic;
}
static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long pp_magic)
{
__netmem_clear_lsb(netmem)->pp_magic |= pp_magic;
}
static inline void netmem_clear_pp_magic(netmem_ref netmem)
{
__netmem_clear_lsb(netmem)->pp_magic = 0;
}
static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool)
{
__netmem_clear_lsb(netmem)->pp = pool;
}
static inline void netmem_set_dma_addr(netmem_ref netmem,
unsigned long dma_addr)
{
__netmem_clear_lsb(netmem)->dma_addr = dma_addr;
}
#endif

25
net/core/page_pool.c
View File

@ -24,8 +24,11 @@
#include <trace/events/page_pool.h>
#include "netmem_priv.h"
#include "page_pool_priv.h"
DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
#define DEFER_TIME (msecs_to_jiffies(1000))
#define DEFER_WARN_INTERVAL (60 * HZ)
@ -358,7 +361,7 @@ static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool)
if (unlikely(!netmem))
break;
if (likely(page_to_nid(netmem_to_page(netmem)) == pref_nid)) {
if (likely(netmem_is_pref_nid(netmem, pref_nid))) {
pool->alloc.cache[pool->alloc.count++] = netmem;
} else {
/* NUMA mismatch;
@ -454,10 +457,8 @@ static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem)
static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
{
struct page *page = netmem_to_page(netmem);
page->pp = pool;
page->pp_magic |= PP_SIGNATURE;
netmem_set_pp(netmem, pool);
netmem_or_pp_magic(netmem, PP_SIGNATURE);
/* Ensuring all pages have been split into one fragment initially:
* page_pool_set_pp_info() is only called once for every page when it
@ -472,10 +473,8 @@ static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
static void page_pool_clear_pp_info(netmem_ref netmem)
{
struct page *page = netmem_to_page(netmem);
page->pp_magic = 0;
page->pp = NULL;
netmem_clear_pp_magic(netmem);
netmem_set_pp(netmem, NULL);
}
static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
@ -692,8 +691,9 @@ static bool page_pool_recycle_in_cache(netmem_ref netmem,
static bool __page_pool_page_can_be_recycled(netmem_ref netmem)
{
return page_ref_count(netmem_to_page(netmem)) == 1 &&
!page_is_pfmemalloc(netmem_to_page(netmem));
return netmem_is_net_iov(netmem) ||
(page_ref_count(netmem_to_page(netmem)) == 1 &&
!page_is_pfmemalloc(netmem_to_page(netmem)));
}
/* If the page refcnt == 1, this will try to recycle the page.
@ -728,6 +728,7 @@ __page_pool_put_page(struct page_pool *pool, netmem_ref netmem,
/* Page found as candidate for recycling */
return netmem;
}
/* Fallback/non-XDP mode: API user have elevated refcnt.
*
* Many drivers split up the page into fragments, and some
@ -949,7 +950,7 @@ static void page_pool_empty_ring(struct page_pool *pool)
/* Empty recycle ring */
while ((netmem = (__force netmem_ref)ptr_ring_consume_bh(&pool->ring))) {
/* Verify the refcnt invariant of cached pages */
if (!(page_ref_count(netmem_to_page(netmem)) == 1))
if (!(netmem_ref_count(netmem) == 1))
pr_crit("%s() page_pool refcnt %d violation\n",
__func__, netmem_ref_count(netmem));

26
net/core/page_pool_priv.h
View File

@ -3,10 +3,36 @@
#ifndef __PAGE_POOL_PRIV_H
#define __PAGE_POOL_PRIV_H
#include <net/page_pool/helpers.h>
#include "netmem_priv.h"
s32 page_pool_inflight(const struct page_pool *pool, bool strict);
int page_pool_list(struct page_pool *pool);
void page_pool_detached(struct page_pool *pool);
void page_pool_unlist(struct page_pool *pool);
static inline bool
page_pool_set_dma_addr_netmem(netmem_ref netmem, dma_addr_t addr)
{
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
netmem_set_dma_addr(netmem, addr >> PAGE_SHIFT);
/* We assume page alignment to shave off bottom bits,
* if this "compression" doesn't work we need to drop.
*/
return addr != (dma_addr_t)netmem_get_dma_addr(netmem)
<< PAGE_SHIFT;
}
netmem_set_dma_addr(netmem, addr);
return false;
}
static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
}
#endif

23
net/core/skbuff.c
View File

@ -88,6 +88,7 @@
#include <linux/textsearch.h>
#include "dev.h"
#include "netmem_priv.h"
#include "sock_destructor.h"
#ifdef CONFIG_SKB_EXTENSIONS
@ -920,9 +921,9 @@ static void skb_clone_fraglist(struct sk_buff *skb)
skb_get(list);
}
static bool is_pp_page(struct page *page)
static bool is_pp_netmem(netmem_ref netmem)
{
return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
}
int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
@ -1020,9 +1021,7 @@ EXPORT_SYMBOL(skb_cow_data_for_xdp);
#if IS_ENABLED(CONFIG_PAGE_POOL)
bool napi_pp_put_page(netmem_ref netmem)
{
struct page *page = netmem_to_page(netmem);
page = compound_head(page);
netmem = netmem_compound_head(netmem);
/* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
* in order to preserve any existing bits, such as bit 0 for the
@ -1031,10 +1030,10 @@ bool napi_pp_put_page(netmem_ref netmem)
* and page_is_pfmemalloc() is checked in __page_pool_put_page()
* to avoid recycling the pfmemalloc page.
*/
if (unlikely(!is_pp_page(page)))
if (unlikely(!is_pp_netmem(netmem)))
return false;
page_pool_put_full_netmem(page->pp, page_to_netmem(page), false);
page_pool_put_full_netmem(netmem_get_pp(netmem), netmem, false);
return true;
}
@ -1061,7 +1060,7 @@ static bool skb_pp_recycle(struct sk_buff *skb, void *data)
static int skb_pp_frag_ref(struct sk_buff *skb)
{
struct skb_shared_info *shinfo;
struct page *head_page;
netmem_ref head_netmem;
int i;
if (!skb->pp_recycle)
@ -1070,11 +1069,11 @@ static int skb_pp_frag_ref(struct sk_buff *skb)
shinfo = skb_shinfo(skb);
for (i = 0; i < shinfo->nr_frags; i++) {
head_page = compound_head(skb_frag_page(&shinfo->frags[i]));
if (likely(is_pp_page(head_page)))
page_pool_ref_page(head_page);
head_netmem = netmem_compound_head(shinfo->frags[i].netmem);
if (likely(is_pp_netmem(head_netmem)))
page_pool_ref_netmem(head_netmem);
else
page_ref_inc(head_page);
page_ref_inc(netmem_to_page(head_netmem));
}
return 0;
}