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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Xen hypercall batching.
4 *
5 * Xen allows multiple hypercalls to be issued at once, using the
6 * multicall interface. This allows the cost of trapping into the
7 * hypervisor to be amortized over several calls.
8 *
9 * This file implements a simple interface for multicalls. There's a
10 * per-cpu buffer of outstanding multicalls. When you want to queue a
11 * multicall for issuing, you can allocate a multicall slot for the
12 * call and its arguments, along with storage for space which is
13 * pointed to by the arguments (for passing pointers to structures,
14 * etc). When the multicall is actually issued, all the space for the
15 * commands and allocated memory is freed for reuse.
16 *
17 * Multicalls are flushed whenever any of the buffers get full, or
18 * when explicitly requested. There's no way to get per-multicall
19 * return results back. It will BUG if any of the multicalls fail.
20 *
21 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
22 */
23#include <linux/percpu.h>
24#include <linux/hardirq.h>
25#include <linux/debugfs.h>
26
27#include <asm/xen/hypercall.h>
28
29#include "multicalls.h"
30#include "debugfs.h"
31
32#define MC_BATCH 32
33
34#define MC_DEBUG 0
35
36#define MC_ARGS (MC_BATCH * 16)
37
38
39struct mc_buffer {
40 unsigned mcidx, argidx, cbidx;
41 struct multicall_entry entries[MC_BATCH];
42#if MC_DEBUG
43 struct multicall_entry debug[MC_BATCH];
44 void *caller[MC_BATCH];
45#endif
46 unsigned char args[MC_ARGS];
47 struct callback {
48 void (*fn)(void *);
49 void *data;
50 } callbacks[MC_BATCH];
51};
52
53static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
54DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
55
56void xen_mc_flush(void)
57{
58 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
59 struct multicall_entry *mc;
60 int ret = 0;
61 unsigned long flags;
62 int i;
63
64 BUG_ON(preemptible());
65
66 /* Disable interrupts in case someone comes in and queues
67 something in the middle */
68 local_irq_save(flags);
69
70 trace_xen_mc_flush(b->mcidx, b->argidx, b->cbidx);
71
72#if MC_DEBUG
73 memcpy(b->debug, b->entries,
74 b->mcidx * sizeof(struct multicall_entry));
75#endif
76
77 switch (b->mcidx) {
78 case 0:
79 /* no-op */
80 BUG_ON(b->argidx != 0);
81 break;
82
83 case 1:
84 /* Singleton multicall - bypass multicall machinery
85 and just do the call directly. */
86 mc = &b->entries[0];
87
88 mc->result = xen_single_call(mc->op, mc->args[0], mc->args[1],
89 mc->args[2], mc->args[3],
90 mc->args[4]);
91 ret = mc->result < 0;
92 break;
93
94 default:
95 if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
96 BUG();
97 for (i = 0; i < b->mcidx; i++)
98 if (b->entries[i].result < 0)
99 ret++;
100 }
101
102 if (WARN_ON(ret)) {
103 pr_err("%d of %d multicall(s) failed: cpu %d\n",
104 ret, b->mcidx, smp_processor_id());
105 for (i = 0; i < b->mcidx; i++) {
106 if (b->entries[i].result < 0) {
107#if MC_DEBUG
108 pr_err(" call %2d: op=%lu arg=[%lx] result=%ld\t%pS\n",
109 i + 1,
110 b->debug[i].op,
111 b->debug[i].args[0],
112 b->entries[i].result,
113 b->caller[i]);
114#else
115 pr_err(" call %2d: op=%lu arg=[%lx] result=%ld\n",
116 i + 1,
117 b->entries[i].op,
118 b->entries[i].args[0],
119 b->entries[i].result);
120#endif
121 }
122 }
123 }
124
125 b->mcidx = 0;
126 b->argidx = 0;
127
128 for (i = 0; i < b->cbidx; i++) {
129 struct callback *cb = &b->callbacks[i];
130
131 (*cb->fn)(cb->data);
132 }
133 b->cbidx = 0;
134
135 local_irq_restore(flags);
136}
137
138struct multicall_space __xen_mc_entry(size_t args)
139{
140 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
141 struct multicall_space ret;
142 unsigned argidx = roundup(b->argidx, sizeof(u64));
143
144 trace_xen_mc_entry_alloc(args);
145
146 BUG_ON(preemptible());
147 BUG_ON(b->argidx >= MC_ARGS);
148
149 if (unlikely(b->mcidx == MC_BATCH ||
150 (argidx + args) >= MC_ARGS)) {
151 trace_xen_mc_flush_reason((b->mcidx == MC_BATCH) ?
152 XEN_MC_FL_BATCH : XEN_MC_FL_ARGS);
153 xen_mc_flush();
154 argidx = roundup(b->argidx, sizeof(u64));
155 }
156
157 ret.mc = &b->entries[b->mcidx];
158#if MC_DEBUG
159 b->caller[b->mcidx] = __builtin_return_address(0);
160#endif
161 b->mcidx++;
162 ret.args = &b->args[argidx];
163 b->argidx = argidx + args;
164
165 BUG_ON(b->argidx >= MC_ARGS);
166 return ret;
167}
168
169struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
170{
171 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
172 struct multicall_space ret = { NULL, NULL };
173
174 BUG_ON(preemptible());
175 BUG_ON(b->argidx >= MC_ARGS);
176
177 if (unlikely(b->mcidx == 0 ||
178 b->entries[b->mcidx - 1].op != op)) {
179 trace_xen_mc_extend_args(op, size, XEN_MC_XE_BAD_OP);
180 goto out;
181 }
182
183 if (unlikely((b->argidx + size) >= MC_ARGS)) {
184 trace_xen_mc_extend_args(op, size, XEN_MC_XE_NO_SPACE);
185 goto out;
186 }
187
188 ret.mc = &b->entries[b->mcidx - 1];
189 ret.args = &b->args[b->argidx];
190 b->argidx += size;
191
192 BUG_ON(b->argidx >= MC_ARGS);
193
194 trace_xen_mc_extend_args(op, size, XEN_MC_XE_OK);
195out:
196 return ret;
197}
198
199void xen_mc_callback(void (*fn)(void *), void *data)
200{
201 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
202 struct callback *cb;
203
204 if (b->cbidx == MC_BATCH) {
205 trace_xen_mc_flush_reason(XEN_MC_FL_CALLBACK);
206 xen_mc_flush();
207 }
208
209 trace_xen_mc_callback(fn, data);
210
211 cb = &b->callbacks[b->cbidx++];
212 cb->fn = fn;
213 cb->data = data;
214}
1/*
2 * Xen hypercall batching.
3 *
4 * Xen allows multiple hypercalls to be issued at once, using the
5 * multicall interface. This allows the cost of trapping into the
6 * hypervisor to be amortized over several calls.
7 *
8 * This file implements a simple interface for multicalls. There's a
9 * per-cpu buffer of outstanding multicalls. When you want to queue a
10 * multicall for issuing, you can allocate a multicall slot for the
11 * call and its arguments, along with storage for space which is
12 * pointed to by the arguments (for passing pointers to structures,
13 * etc). When the multicall is actually issued, all the space for the
14 * commands and allocated memory is freed for reuse.
15 *
16 * Multicalls are flushed whenever any of the buffers get full, or
17 * when explicitly requested. There's no way to get per-multicall
18 * return results back. It will BUG if any of the multicalls fail.
19 *
20 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
21 */
22#include <linux/percpu.h>
23#include <linux/hardirq.h>
24#include <linux/debugfs.h>
25
26#include <asm/xen/hypercall.h>
27
28#include "multicalls.h"
29#include "debugfs.h"
30
31#define MC_BATCH 32
32
33#define MC_DEBUG 0
34
35#define MC_ARGS (MC_BATCH * 16)
36
37
38struct mc_buffer {
39 unsigned mcidx, argidx, cbidx;
40 struct multicall_entry entries[MC_BATCH];
41#if MC_DEBUG
42 struct multicall_entry debug[MC_BATCH];
43 void *caller[MC_BATCH];
44#endif
45 unsigned char args[MC_ARGS];
46 struct callback {
47 void (*fn)(void *);
48 void *data;
49 } callbacks[MC_BATCH];
50};
51
52static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
53DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
54
55void xen_mc_flush(void)
56{
57 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
58 struct multicall_entry *mc;
59 int ret = 0;
60 unsigned long flags;
61 int i;
62
63 BUG_ON(preemptible());
64
65 /* Disable interrupts in case someone comes in and queues
66 something in the middle */
67 local_irq_save(flags);
68
69 trace_xen_mc_flush(b->mcidx, b->argidx, b->cbidx);
70
71 switch (b->mcidx) {
72 case 0:
73 /* no-op */
74 BUG_ON(b->argidx != 0);
75 break;
76
77 case 1:
78 /* Singleton multicall - bypass multicall machinery
79 and just do the call directly. */
80 mc = &b->entries[0];
81
82 mc->result = privcmd_call(mc->op,
83 mc->args[0], mc->args[1], mc->args[2],
84 mc->args[3], mc->args[4]);
85 ret = mc->result < 0;
86 break;
87
88 default:
89#if MC_DEBUG
90 memcpy(b->debug, b->entries,
91 b->mcidx * sizeof(struct multicall_entry));
92#endif
93
94 if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
95 BUG();
96 for (i = 0; i < b->mcidx; i++)
97 if (b->entries[i].result < 0)
98 ret++;
99
100#if MC_DEBUG
101 if (ret) {
102 printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
103 ret, smp_processor_id());
104 dump_stack();
105 for (i = 0; i < b->mcidx; i++) {
106 printk(KERN_DEBUG " call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
107 i+1, b->mcidx,
108 b->debug[i].op,
109 b->debug[i].args[0],
110 b->entries[i].result,
111 b->caller[i]);
112 }
113 }
114#endif
115 }
116
117 b->mcidx = 0;
118 b->argidx = 0;
119
120 for (i = 0; i < b->cbidx; i++) {
121 struct callback *cb = &b->callbacks[i];
122
123 (*cb->fn)(cb->data);
124 }
125 b->cbidx = 0;
126
127 local_irq_restore(flags);
128
129 WARN_ON(ret);
130}
131
132struct multicall_space __xen_mc_entry(size_t args)
133{
134 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
135 struct multicall_space ret;
136 unsigned argidx = roundup(b->argidx, sizeof(u64));
137
138 trace_xen_mc_entry_alloc(args);
139
140 BUG_ON(preemptible());
141 BUG_ON(b->argidx >= MC_ARGS);
142
143 if (unlikely(b->mcidx == MC_BATCH ||
144 (argidx + args) >= MC_ARGS)) {
145 trace_xen_mc_flush_reason((b->mcidx == MC_BATCH) ?
146 XEN_MC_FL_BATCH : XEN_MC_FL_ARGS);
147 xen_mc_flush();
148 argidx = roundup(b->argidx, sizeof(u64));
149 }
150
151 ret.mc = &b->entries[b->mcidx];
152#if MC_DEBUG
153 b->caller[b->mcidx] = __builtin_return_address(0);
154#endif
155 b->mcidx++;
156 ret.args = &b->args[argidx];
157 b->argidx = argidx + args;
158
159 BUG_ON(b->argidx >= MC_ARGS);
160 return ret;
161}
162
163struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
164{
165 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
166 struct multicall_space ret = { NULL, NULL };
167
168 BUG_ON(preemptible());
169 BUG_ON(b->argidx >= MC_ARGS);
170
171 if (unlikely(b->mcidx == 0 ||
172 b->entries[b->mcidx - 1].op != op)) {
173 trace_xen_mc_extend_args(op, size, XEN_MC_XE_BAD_OP);
174 goto out;
175 }
176
177 if (unlikely((b->argidx + size) >= MC_ARGS)) {
178 trace_xen_mc_extend_args(op, size, XEN_MC_XE_NO_SPACE);
179 goto out;
180 }
181
182 ret.mc = &b->entries[b->mcidx - 1];
183 ret.args = &b->args[b->argidx];
184 b->argidx += size;
185
186 BUG_ON(b->argidx >= MC_ARGS);
187
188 trace_xen_mc_extend_args(op, size, XEN_MC_XE_OK);
189out:
190 return ret;
191}
192
193void xen_mc_callback(void (*fn)(void *), void *data)
194{
195 struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
196 struct callback *cb;
197
198 if (b->cbidx == MC_BATCH) {
199 trace_xen_mc_flush_reason(XEN_MC_FL_CALLBACK);
200 xen_mc_flush();
201 }
202
203 trace_xen_mc_callback(fn, data);
204
205 cb = &b->callbacks[b->cbidx++];
206 cb->fn = fn;
207 cb->data = data;
208}