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 "qemu-common.h"
28 #include "sysemu/tcg.h"
29 #include "sysemu/replay.h"
30 #include "qemu/main-loop.h"
31 #include "qemu/guest-random.h"
32 #include "exec/exec-all.h"
33 #include "hw/boards.h"
34 
35 #include "tcg-accel-ops.h"
36 #include "tcg-accel-ops-icount.h"
37 #include "tcg-accel-ops-rr.h"
38 
39 static int64_t icount_get_limit(void)
40 {
41     int64_t deadline;
42 
43     if (replay_mode != REPLAY_MODE_PLAY) {
44         /*
45          * Include all the timers, because they may need an attention.
46          * Too long CPU execution may create unnecessary delay in UI.
47          */
48         deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
49                                               QEMU_TIMER_ATTR_ALL);
50         /* Check realtime timers, because they help with input processing */
51         deadline = qemu_soonest_timeout(deadline,
52                 qemu_clock_deadline_ns_all(QEMU_CLOCK_REALTIME,
53                                            QEMU_TIMER_ATTR_ALL));
54 
55         /*
56          * Maintain prior (possibly buggy) behaviour where if no deadline
57          * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
58          * INT32_MAX nanoseconds ahead, we still use INT32_MAX
59          * nanoseconds.
60          */
61         if ((deadline < 0) || (deadline > INT32_MAX)) {
62             deadline = INT32_MAX;
63         }
64 
65         return icount_round(deadline);
66     } else {
67         return replay_get_instructions();
68     }
69 }
70 
71 static void icount_notify_aio_contexts(void)
72 {
73     /* Wake up other AioContexts.  */
74     qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
75     qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
76 }
77 
78 void icount_handle_deadline(void)
79 {
80     assert(qemu_in_vcpu_thread());
81     int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
82                                                   QEMU_TIMER_ATTR_ALL);
83 
84     /*
85      * Instructions, interrupts, and exceptions are processed in cpu-exec.
86      * Don't interrupt cpu thread, when these events are waiting
87      * (i.e., there is no checkpoint)
88      */
89     if (deadline == 0
90         && (replay_mode != REPLAY_MODE_PLAY || replay_has_checkpoint())) {
91         icount_notify_aio_contexts();
92     }
93 }
94 
95 void icount_prepare_for_run(CPUState *cpu)
96 {
97     int insns_left;
98 
99     /*
100      * These should always be cleared by icount_process_data after
101      * each vCPU execution. However u16.high can be raised
102      * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt
103      */
104     g_assert(cpu_neg(cpu)->icount_decr.u16.low == 0);
105     g_assert(cpu->icount_extra == 0);
106 
107     cpu->icount_budget = icount_get_limit();
108     insns_left = MIN(0xffff, cpu->icount_budget);
109     cpu_neg(cpu)->icount_decr.u16.low = insns_left;
110     cpu->icount_extra = cpu->icount_budget - insns_left;
111 
112     replay_mutex_lock();
113 
114     if (cpu->icount_budget == 0 && replay_has_checkpoint()) {
115         icount_notify_aio_contexts();
116     }
117 }
118 
119 void icount_process_data(CPUState *cpu)
120 {
121     /* Account for executed instructions */
122     icount_update(cpu);
123 
124     /* Reset the counters */
125     cpu_neg(cpu)->icount_decr.u16.low = 0;
126     cpu->icount_extra = 0;
127     cpu->icount_budget = 0;
128 
129     replay_account_executed_instructions();
130 
131     replay_mutex_unlock();
132 }
133 
134 void icount_handle_interrupt(CPUState *cpu, int mask)
135 {
136     int old_mask = cpu->interrupt_request;
137 
138     tcg_handle_interrupt(cpu, mask);
139     if (qemu_cpu_is_self(cpu) &&
140         !cpu->can_do_io
141         && (mask & ~old_mask) != 0) {
142         cpu_abort(cpu, "Raised interrupt while not in I/O function");
143     }
144 }
145