@samitouri / QOSamiQemu
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1 /*
2 * QEMU TCG Single Threaded vCPUs implementation using instruction counting
3 *
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 * Copyright (c) 2014 Red Hat Inc.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23 * THE SOFTWARE.
24 */
25
26 #include "qemu/osdep.h"
27 #include "system/replay.h"
28 #include "exec/icount.h"
29 #include "qemu/main-loop.h"
30 #include "qemu/guest-random.h"
31 #include "hw/core/cpu.h"
32
33 #include "tcg-accel-ops.h"
34 #include "tcg-accel-ops-icount.h"
35 #include "tcg-accel-ops-rr.h"
36
37 static int64_t icount_get_limit(void)
38 {
39 int64_t deadline;
40
41 if (replay_mode != REPLAY_MODE_PLAY) {
42 /*
43 * Include all the timers, because they may need an attention.
44 * Too long CPU execution may create unnecessary delay in UI.
45 */
46 deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
47 QEMU_TIMER_ATTR_ALL);
48 /* Check realtime timers, because they help with input processing */
49 deadline = qemu_soonest_timeout(deadline,
50 qemu_clock_deadline_ns_all(QEMU_CLOCK_REALTIME,
51 QEMU_TIMER_ATTR_ALL));
52
53 /*
54 * Maintain prior (possibly buggy) behaviour where if no deadline
55 * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
56 * INT32_MAX nanoseconds ahead, we still use INT32_MAX
57 * nanoseconds.
58 */
59 if ((deadline < 0) || (deadline > INT32_MAX)) {
60 deadline = INT32_MAX;
61 }
62
63 return icount_round(deadline);
64 } else {
65 return replay_get_instructions();
66 }
67 }
68
69 static void icount_notify_aio_contexts(void)
70 {
71 /* Wake up other AioContexts. */
72 qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
73 qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
74 }
75
76 void icount_handle_deadline(void)
77 {
78 assert(qemu_in_vcpu_thread());
79 int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
80 QEMU_TIMER_ATTR_ALL);
81
82 /*
83 * Instructions, interrupts, and exceptions are processed in cpu-exec.
84 * Don't interrupt cpu thread, when these events are waiting
85 * (i.e., there is no checkpoint)
86 */
87 if (deadline == 0) {
88 icount_notify_aio_contexts();
89 }
90 }
91
92 /* Distribute the budget evenly across all CPUs */
93 int64_t icount_percpu_budget(int cpu_count)
94 {
95 int64_t limit = icount_get_limit();
96 int64_t timeslice = limit / cpu_count;
97
98 if (timeslice == 0) {
99 timeslice = limit;
100 }
101
102 return timeslice;
103 }
104
105 void icount_prepare_for_run(CPUState *cpu, int64_t cpu_budget)
106 {
107 int insns_left;
108
109 /*
110 * These should always be cleared by icount_process_data after
111 * each vCPU execution. However u16.high can be raised
112 * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt
113 */
114 g_assert(cpu->neg.icount_decr.u16.low == 0);
115 g_assert(cpu->icount_extra == 0);
116
117 replay_mutex_lock();
118
119 cpu->icount_budget = MIN(icount_get_limit(), cpu_budget);
120 insns_left = MIN(0xffff, cpu->icount_budget);
121 cpu->neg.icount_decr.u16.low = insns_left;
122 cpu->icount_extra = cpu->icount_budget - insns_left;
123
124 if (cpu->icount_budget == 0) {
125 /*
126 * We're called without the BQL, so must take it while
127 * we're calling timer handlers.
128 */
129 bql_lock();
130 icount_notify_aio_contexts();
131 bql_unlock();
132 }
133 }
134
135 void icount_process_data(CPUState *cpu)
136 {
137 /* Account for executed instructions */
138 icount_update(cpu);
139
140 /* Reset the counters */
141 cpu->neg.icount_decr.u16.low = 0;
142 cpu->icount_extra = 0;
143 cpu->icount_budget = 0;
144
145 replay_account_executed_instructions();
146
147 replay_mutex_unlock();
148 }
149
150 void icount_handle_interrupt(CPUState *cpu, int mask)
151 {
152 int old_mask = cpu->interrupt_request;
153
154 tcg_handle_interrupt(cpu, mask);
155 if (qemu_cpu_is_self(cpu) &&
156 !cpu->neg.can_do_io
157 && (mask & ~old_mask) != 0) {
158 cpu_abort(cpu, "Raised interrupt while not in I/O function");
159 }
160 }