1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_ASM_ASID_H
3 #define __ASM_ASM_ASID_H
4
5 #include <linux/atomic.h>
6 #include <linux/compiler.h>
7 #include <linux/cpumask.h>
8 #include <linux/percpu.h>
9 #include <linux/spinlock.h>
10
11 struct asid_info
12 {
13 atomic64_t generation;
14 unsigned long *map;
15 atomic64_t __percpu *active;
16 u64 __percpu *reserved;
17 u32 bits;
18 /* Lock protecting the structure */
19 raw_spinlock_t lock;
20 /* Which CPU requires context flush on next call */
21 cpumask_t flush_pending;
22 /* Number of ASID allocated by context (shift value) */
23 unsigned int ctxt_shift;
24 /* Callback to locally flush the context. */
25 void (*flush_cpu_ctxt_cb)(void);
26 };
27
28 #define NUM_ASIDS(info) (1UL << ((info)->bits))
29 #define NUM_CTXT_ASIDS(info) (NUM_ASIDS(info) >> (info)->ctxt_shift)
30
31 #define active_asid(info, cpu) *per_cpu_ptr((info)->active, cpu)
32
33 void asid_new_context(struct asid_info *info, atomic64_t *pasid,
34 unsigned int cpu, struct mm_struct *mm);
35
36 /*
37 * Check the ASID is still valid for the context. If not generate a new ASID.
38 *
39 * @pasid: Pointer to the current ASID batch
40 * @cpu: current CPU ID. Must have been acquired through get_cpu()
41 */
42 static inline void asid_check_context(struct asid_info *info,
43 atomic64_t *pasid, unsigned int cpu,
44 struct mm_struct *mm)
45 {
46 u64 asid, old_active_asid;
47
48 asid = atomic64_read(pasid);
49
50 /*
51 * The memory ordering here is subtle.
52 * If our active_asid is non-zero and the ASID matches the current
53 * generation, then we update the active_asid entry with a relaxed
54 * cmpxchg. Racing with a concurrent rollover means that either:
55 *
56 * - We get a zero back from the cmpxchg and end up waiting on the
57 * lock. Taking the lock synchronises with the rollover and so
58 * we are forced to see the updated generation.
59 *
60 * - We get a valid ASID back from the cmpxchg, which means the
61 * relaxed xchg in flush_context will treat us as reserved
62 * because atomic RmWs are totally ordered for a given location.
63 */
64 old_active_asid = atomic64_read(&active_asid(info, cpu));
65 if (old_active_asid &&
66 !((asid ^ atomic64_read(&info->generation)) >> info->bits) &&
67 atomic64_cmpxchg_relaxed(&active_asid(info, cpu),
68 old_active_asid, asid))
69 return;
70
71 asid_new_context(info, pasid, cpu, mm);
72 }
73
74 int asid_allocator_init(struct asid_info *info,
75 u32 bits, unsigned int asid_per_ctxt,
76 void (*flush_cpu_ctxt_cb)(void));
77
78 #endif
79
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