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1/* SPDX-License-Identifier: GPL-2.0
2 *
3 * Network memory
4 *
5 * Author: Mina Almasry <almasrymina@google.com>
6 */
7
8#ifndef _NET_NETMEM_H
9#define _NET_NETMEM_H
10
11#include <linux/mm.h>
12#include <net/net_debug.h>
13
14/* net_iov */
15
16DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
17
18/* We overload the LSB of the struct page pointer to indicate whether it's
19 * a page or net_iov.
20 */
21#define NET_IOV 0x01UL
22
23struct net_iov {
24 unsigned long __unused_padding;
25 unsigned long pp_magic;
26 struct page_pool *pp;
27 struct dmabuf_genpool_chunk_owner *owner;
28 unsigned long dma_addr;
29 atomic_long_t pp_ref_count;
30};
31
32/* These fields in struct page are used by the page_pool and net stack:
33 *
34 * struct {
35 * unsigned long pp_magic;
36 * struct page_pool *pp;
37 * unsigned long _pp_mapping_pad;
38 * unsigned long dma_addr;
39 * atomic_long_t pp_ref_count;
40 * };
41 *
42 * We mirror the page_pool fields here so the page_pool can access these fields
43 * without worrying whether the underlying fields belong to a page or net_iov.
44 *
45 * The non-net stack fields of struct page are private to the mm stack and must
46 * never be mirrored to net_iov.
47 */
48#define NET_IOV_ASSERT_OFFSET(pg, iov) \
49 static_assert(offsetof(struct page, pg) == \
50 offsetof(struct net_iov, iov))
51NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);
52NET_IOV_ASSERT_OFFSET(pp, pp);
53NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);
54NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
55#undef NET_IOV_ASSERT_OFFSET
56
57/* netmem */
58
59/**
60 * typedef netmem_ref - a nonexistent type marking a reference to generic
61 * network memory.
62 *
63 * A netmem_ref currently is always a reference to a struct page. This
64 * abstraction is introduced so support for new memory types can be added.
65 *
66 * Use the supplied helpers to obtain the underlying memory pointer and fields.
67 */
68typedef unsigned long __bitwise netmem_ref;
69
70static inline bool netmem_is_net_iov(const netmem_ref netmem)
71{
72 return (__force unsigned long)netmem & NET_IOV;
73}
74
75/* This conversion fails (returns NULL) if the netmem_ref is not struct page
76 * backed.
77 */
78static inline struct page *netmem_to_page(netmem_ref netmem)
79{
80 if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
81 return NULL;
82
83 return (__force struct page *)netmem;
84}
85
86static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
87{
88 if (netmem_is_net_iov(netmem))
89 return (struct net_iov *)((__force unsigned long)netmem &
90 ~NET_IOV);
91
92 DEBUG_NET_WARN_ON_ONCE(true);
93 return NULL;
94}
95
96static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
97{
98 return (__force netmem_ref)((unsigned long)niov | NET_IOV);
99}
100
101static inline netmem_ref page_to_netmem(struct page *page)
102{
103 return (__force netmem_ref)page;
104}
105
106static inline int netmem_ref_count(netmem_ref netmem)
107{
108 /* The non-pp refcount of net_iov is always 1. On net_iov, we only
109 * support pp refcounting which uses the pp_ref_count field.
110 */
111 if (netmem_is_net_iov(netmem))
112 return 1;
113
114 return page_ref_count(netmem_to_page(netmem));
115}
116
117static inline unsigned long netmem_pfn_trace(netmem_ref netmem)
118{
119 if (netmem_is_net_iov(netmem))
120 return 0;
121
122 return page_to_pfn(netmem_to_page(netmem));
123}
124
125static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
126{
127 return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);
128}
129
130static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
131{
132 return __netmem_clear_lsb(netmem)->pp;
133}
134
135static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
136{
137 return &__netmem_clear_lsb(netmem)->pp_ref_count;
138}
139
140static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
141{
142 /* NUMA node preference only makes sense if we're allocating
143 * system memory. Memory providers (which give us net_iovs)
144 * choose for us.
145 */
146 if (netmem_is_net_iov(netmem))
147 return true;
148
149 return page_to_nid(netmem_to_page(netmem)) == pref_nid;
150}
151
152static inline netmem_ref netmem_compound_head(netmem_ref netmem)
153{
154 /* niov are never compounded */
155 if (netmem_is_net_iov(netmem))
156 return netmem;
157
158 return page_to_netmem(compound_head(netmem_to_page(netmem)));
159}
160
161static inline void *netmem_address(netmem_ref netmem)
162{
163 if (netmem_is_net_iov(netmem))
164 return NULL;
165
166 return page_address(netmem_to_page(netmem));
167}
168
169static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
170{
171 return __netmem_clear_lsb(netmem)->dma_addr;
172}
173
174#endif /* _NET_NETMEM_H */