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![Emilio G. Cota](/assets/img/avatar_default.png)
Having a fixed-size hash table for keeping track of all translation blocks is suboptimal: some workloads are just too big or too small to get maximum performance from the hash table. The MRU promotion policy helps improve performance when the hash table is a little undersized, but it cannot make up for severely undersized hash tables. Furthermore, frequent MRU promotions result in writes that are a scalability bottleneck. For scalability, lookups should only perform reads, not writes. This is not a big deal for now, but it will become one once MTTCG matures. The appended fixes these issues by using qht as the implementation of the TB hash table. This solution is superior to other alternatives considered, namely: - master: implementation in QEMU before this patchset - xxhash: before this patch, i.e. fixed buckets + xxhash hashing + MRU. - xxhash-rcu: fixed buckets + xxhash + RCU list + MRU. MRU is implemented here by adding an intermediate struct that contains the u32 hash and a pointer to the TB; this allows us, on an MRU promotion, to copy said struct (that is not at the head), and put this new copy at the head. After a grace period, the original non-head struct can be eliminated, and after another grace period, freed. - qht-fixed-nomru: fixed buckets + xxhash + qht without auto-resize + no MRU for lookups; MRU for inserts. The appended solution is the following: - qht-dyn-nomru: dynamic number of buckets + xxhash + qht w/ auto-resize + no MRU for lookups; MRU for inserts. The plots below compare the considered solutions. The Y axis shows the boot time (in seconds) of a debian jessie image with arm-softmmu; the X axis sweeps the number of buckets (or initial number of buckets for qht-autoresize). The plots in PNG format (and with errorbars) can be seen here: http://imgur.com/a/Awgnq Each test runs 5 times, and the entire QEMU process is pinned to a single core for repeatability of results. Host: Intel Xeon E5-2690 28 ++------------+-------------+-------------+-------------+------------++ A***** + + + master **A*** + 27 ++ * xxhash ##B###++ | A******A****** xxhash-rcu $$C$$$ | 26 C$$ A******A****** qht-fixed-nomru*%%D%%%++ D%%$$ A******A******A*qht-dyn-mru A*E****A 25 ++ %%$$ qht-dyn-nomru &&F&&&++ B#####% | 24 ++ #C$$$$$ ++ | B### $ | | ## C$$$$$$ | 23 ++ # C$$$$$$ ++ | B###### C$$$$$$ %%%D 22 ++ %B###### C$$$$$$C$$$$$$C$$$$$$C$$$$$$C$$$$$$C | D%%%%%%B###### @E@@@@@@ %%%D%%%@@@E@@@@@@E 21 E@@@@@@E@@@@@@F&&&@@@E@@@&&&D%%%%%%B######B######B######B######B######B + E@@@ F&&& + E@ + F&&& + + 20 ++------------+-------------+-------------+-------------+------------++ 14 16 18 20 22 24 log2 number of buckets Host: Intel i7-4790K 14.5 ++------------+------------+-------------+------------+------------++ A** + + + master **A*** + 14 ++ ** xxhash ##B###++ 13.5 ++ ** xxhash-rcu $$C$$$++ | qht-fixed-nomru %%D%%% | 13 ++ A****** qht-dyn-mru @@E@@@++ | A*****A******A****** qht-dyn-nomru &&F&&& | 12.5 C$$ A******A******A*****A****** ***A 12 ++ $$ A*** ++ D%%% $$ | 11.5 ++ %% ++ B### %C$$$$$$ | 11 ++ ## D%%%%% C$$$$$ ++ | # % C$$$$$$ | 10.5 F&&&&&&B######D%%%%% C$$$$$$C$$$$$$C$$$$$$C$$$$$C$$$$$$ $$$C 10 E@@@@@@E@@@@@@B#####B######B######E@@@@@@E@@@%%%D%%%%%D%%%###B######B + F&& D%%%%%%B######B######B#####B###@@@D%%% + 9.5 ++------------+------------+-------------+------------+------------++ 14 16 18 20 22 24 log2 number of buckets Note that the original point before this patch series is X=15 for "master"; the little sensitivity to the increased number of buckets is due to the poor hashing function in master. xxhash-rcu has significant overhead due to the constant churn of allocating and deallocating intermediate structs for implementing MRU. An alternative would be do consider failed lookups as "maybe not there", and then acquire the external lock (tb_lock in this case) to really confirm that there was indeed a failed lookup. This, however, would not be enough to implement dynamic resizing--this is more complex: see "Resizable, Scalable, Concurrent Hash Tables via Relativistic Programming" by Triplett, McKenney and Walpole. This solution was discarded due to the very coarse RCU read critical sections that we have in MTTCG; resizing requires waiting for readers after every pointer update, and resizes require many pointer updates, so this would quickly become prohibitive. qht-fixed-nomru shows that MRU promotion is advisable for undersized hash tables. However, qht-dyn-mru shows that MRU promotion is not important if the hash table is properly sized: there is virtually no difference in performance between qht-dyn-nomru and qht-dyn-mru. Before this patch, we're at X=15 on "xxhash"; after this patch, we're at X=15 @ qht-dyn-nomru. This patch thus matches the best performance that we can achieve with optimum sizing of the hash table, while keeping the hash table scalable for readers. The improvement we get before and after this patch for booting debian jessie with arm-softmmu is: - Intel Xeon E5-2690: 10.5% less time - Intel i7-4790K: 5.2% less time We could get this same improvement _for this particular workload_ by statically increasing the size of the hash table. But this would hurt workloads that do not need a large hash table. The dynamic (upward) resizing allows us to start small and enlarge the hash table as needed. A quick note on downsizing: the table is resized back to 2**15 buckets on every tb_flush; this makes sense because it is not guaranteed that the table will reach the same number of TBs later on (e.g. most bootup code is thrown away after boot); it makes sense to grow the hash table as more code blocks are translated. This also avoids the complication of having to build downsizing hysteresis logic into qht. Reviewed-by: Sergey Fedorov <serge.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <1465412133-3029-15-git-send-email-cota@braap.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
659 lines
20 KiB
C
659 lines
20 KiB
C
/*
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* emulator main execution loop
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*
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* Copyright (c) 2003-2005 Fabrice Bellard
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include "qemu/osdep.h"
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#include "cpu.h"
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#include "trace.h"
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#include "disas/disas.h"
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#include "exec/exec-all.h"
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#include "tcg.h"
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#include "qemu/atomic.h"
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#include "sysemu/qtest.h"
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#include "qemu/timer.h"
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#include "exec/address-spaces.h"
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#include "qemu/rcu.h"
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#include "exec/tb-hash.h"
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#include "exec/log.h"
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#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
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#include "hw/i386/apic.h"
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#endif
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#include "sysemu/replay.h"
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/* -icount align implementation. */
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typedef struct SyncClocks {
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int64_t diff_clk;
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int64_t last_cpu_icount;
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int64_t realtime_clock;
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} SyncClocks;
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#if !defined(CONFIG_USER_ONLY)
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/* Allow the guest to have a max 3ms advance.
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* The difference between the 2 clocks could therefore
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* oscillate around 0.
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*/
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#define VM_CLOCK_ADVANCE 3000000
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#define THRESHOLD_REDUCE 1.5
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#define MAX_DELAY_PRINT_RATE 2000000000LL
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#define MAX_NB_PRINTS 100
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static void align_clocks(SyncClocks *sc, const CPUState *cpu)
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{
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int64_t cpu_icount;
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if (!icount_align_option) {
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return;
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}
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cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
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sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
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sc->last_cpu_icount = cpu_icount;
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if (sc->diff_clk > VM_CLOCK_ADVANCE) {
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#ifndef _WIN32
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struct timespec sleep_delay, rem_delay;
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sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
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sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
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if (nanosleep(&sleep_delay, &rem_delay) < 0) {
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sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec;
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} else {
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sc->diff_clk = 0;
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}
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#else
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Sleep(sc->diff_clk / SCALE_MS);
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sc->diff_clk = 0;
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#endif
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}
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}
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static void print_delay(const SyncClocks *sc)
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{
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static float threshold_delay;
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static int64_t last_realtime_clock;
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static int nb_prints;
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if (icount_align_option &&
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sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
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nb_prints < MAX_NB_PRINTS) {
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if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
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(-sc->diff_clk / (float)1000000000LL <
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(threshold_delay - THRESHOLD_REDUCE))) {
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threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
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printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
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threshold_delay - 1,
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threshold_delay);
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nb_prints++;
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last_realtime_clock = sc->realtime_clock;
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}
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}
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}
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static void init_delay_params(SyncClocks *sc,
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const CPUState *cpu)
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{
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if (!icount_align_option) {
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return;
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}
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sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
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sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
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sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
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if (sc->diff_clk < max_delay) {
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max_delay = sc->diff_clk;
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}
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if (sc->diff_clk > max_advance) {
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max_advance = sc->diff_clk;
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}
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/* Print every 2s max if the guest is late. We limit the number
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of printed messages to NB_PRINT_MAX(currently 100) */
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print_delay(sc);
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}
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#else
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static void align_clocks(SyncClocks *sc, const CPUState *cpu)
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{
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}
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static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
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{
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}
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#endif /* CONFIG USER ONLY */
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/* Execute a TB, and fix up the CPU state afterwards if necessary */
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static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
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{
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CPUArchState *env = cpu->env_ptr;
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uintptr_t ret;
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TranslationBlock *last_tb;
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int tb_exit;
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uint8_t *tb_ptr = itb->tc_ptr;
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qemu_log_mask_and_addr(CPU_LOG_EXEC, itb->pc,
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"Trace %p [" TARGET_FMT_lx "] %s\n",
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itb->tc_ptr, itb->pc, lookup_symbol(itb->pc));
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#if defined(DEBUG_DISAS)
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if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
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#if defined(TARGET_I386)
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log_cpu_state(cpu, CPU_DUMP_CCOP);
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#elif defined(TARGET_M68K)
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/* ??? Should not modify env state for dumping. */
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cpu_m68k_flush_flags(env, env->cc_op);
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env->cc_op = CC_OP_FLAGS;
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env->sr = (env->sr & 0xffe0) | env->cc_dest | (env->cc_x << 4);
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log_cpu_state(cpu, 0);
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#else
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log_cpu_state(cpu, 0);
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#endif
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}
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#endif /* DEBUG_DISAS */
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cpu->can_do_io = !use_icount;
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ret = tcg_qemu_tb_exec(env, tb_ptr);
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cpu->can_do_io = 1;
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last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
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tb_exit = ret & TB_EXIT_MASK;
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trace_exec_tb_exit(last_tb, tb_exit);
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if (tb_exit > TB_EXIT_IDX1) {
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/* We didn't start executing this TB (eg because the instruction
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* counter hit zero); we must restore the guest PC to the address
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* of the start of the TB.
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*/
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CPUClass *cc = CPU_GET_CLASS(cpu);
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qemu_log_mask_and_addr(CPU_LOG_EXEC, last_tb->pc,
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"Stopped execution of TB chain before %p ["
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TARGET_FMT_lx "] %s\n",
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last_tb->tc_ptr, last_tb->pc,
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lookup_symbol(last_tb->pc));
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if (cc->synchronize_from_tb) {
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cc->synchronize_from_tb(cpu, last_tb);
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} else {
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assert(cc->set_pc);
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cc->set_pc(cpu, last_tb->pc);
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}
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}
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if (tb_exit == TB_EXIT_REQUESTED) {
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/* We were asked to stop executing TBs (probably a pending
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* interrupt. We've now stopped, so clear the flag.
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*/
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cpu->tcg_exit_req = 0;
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}
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return ret;
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}
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#ifndef CONFIG_USER_ONLY
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/* Execute the code without caching the generated code. An interpreter
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could be used if available. */
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static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
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TranslationBlock *orig_tb, bool ignore_icount)
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{
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TranslationBlock *tb;
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bool old_tb_flushed;
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/* Should never happen.
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We only end up here when an existing TB is too long. */
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if (max_cycles > CF_COUNT_MASK)
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max_cycles = CF_COUNT_MASK;
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old_tb_flushed = cpu->tb_flushed;
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cpu->tb_flushed = false;
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tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
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max_cycles | CF_NOCACHE
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| (ignore_icount ? CF_IGNORE_ICOUNT : 0));
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tb->orig_tb = cpu->tb_flushed ? NULL : orig_tb;
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cpu->tb_flushed |= old_tb_flushed;
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/* execute the generated code */
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trace_exec_tb_nocache(tb, tb->pc);
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cpu_tb_exec(cpu, tb);
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tb_phys_invalidate(tb, -1);
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tb_free(tb);
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}
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#endif
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struct tb_desc {
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target_ulong pc;
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target_ulong cs_base;
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CPUArchState *env;
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tb_page_addr_t phys_page1;
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uint32_t flags;
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};
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static bool tb_cmp(const void *p, const void *d)
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{
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const TranslationBlock *tb = p;
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const struct tb_desc *desc = d;
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if (tb->pc == desc->pc &&
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tb->page_addr[0] == desc->phys_page1 &&
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tb->cs_base == desc->cs_base &&
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tb->flags == desc->flags) {
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/* check next page if needed */
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if (tb->page_addr[1] == -1) {
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return true;
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} else {
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tb_page_addr_t phys_page2;
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target_ulong virt_page2;
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virt_page2 = (desc->pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
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phys_page2 = get_page_addr_code(desc->env, virt_page2);
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if (tb->page_addr[1] == phys_page2) {
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return true;
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}
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}
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}
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return false;
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}
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static TranslationBlock *tb_find_physical(CPUState *cpu,
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target_ulong pc,
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target_ulong cs_base,
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uint32_t flags)
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{
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tb_page_addr_t phys_pc;
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struct tb_desc desc;
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uint32_t h;
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desc.env = (CPUArchState *)cpu->env_ptr;
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desc.cs_base = cs_base;
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desc.flags = flags;
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desc.pc = pc;
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phys_pc = get_page_addr_code(desc.env, pc);
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desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
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h = tb_hash_func(phys_pc, pc, flags);
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return qht_lookup(&tcg_ctx.tb_ctx.htable, tb_cmp, &desc, h);
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}
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static TranslationBlock *tb_find_slow(CPUState *cpu,
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target_ulong pc,
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target_ulong cs_base,
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uint32_t flags)
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{
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TranslationBlock *tb;
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tb = tb_find_physical(cpu, pc, cs_base, flags);
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if (tb) {
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goto found;
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}
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#ifdef CONFIG_USER_ONLY
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/* mmap_lock is needed by tb_gen_code, and mmap_lock must be
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* taken outside tb_lock. Since we're momentarily dropping
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* tb_lock, there's a chance that our desired tb has been
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* translated.
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*/
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tb_unlock();
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mmap_lock();
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tb_lock();
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tb = tb_find_physical(cpu, pc, cs_base, flags);
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if (tb) {
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mmap_unlock();
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goto found;
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}
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#endif
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/* if no translated code available, then translate it now */
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tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
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#ifdef CONFIG_USER_ONLY
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mmap_unlock();
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#endif
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found:
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/* we add the TB in the virtual pc hash table */
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cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
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return tb;
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}
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static inline TranslationBlock *tb_find_fast(CPUState *cpu,
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TranslationBlock **last_tb,
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int tb_exit)
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{
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CPUArchState *env = (CPUArchState *)cpu->env_ptr;
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TranslationBlock *tb;
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target_ulong cs_base, pc;
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uint32_t flags;
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/* we record a subset of the CPU state. It will
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always be the same before a given translated block
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is executed. */
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cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
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tb_lock();
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tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
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if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
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tb->flags != flags)) {
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tb = tb_find_slow(cpu, pc, cs_base, flags);
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}
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if (cpu->tb_flushed) {
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/* Ensure that no TB jump will be modified as the
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* translation buffer has been flushed.
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*/
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*last_tb = NULL;
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cpu->tb_flushed = false;
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}
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#ifndef CONFIG_USER_ONLY
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/* We don't take care of direct jumps when address mapping changes in
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* system emulation. So it's not safe to make a direct jump to a TB
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* spanning two pages because the mapping for the second page can change.
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*/
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if (tb->page_addr[1] != -1) {
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*last_tb = NULL;
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}
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#endif
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/* See if we can patch the calling TB. */
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if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
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tb_add_jump(*last_tb, tb_exit, tb);
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}
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tb_unlock();
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return tb;
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}
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static inline bool cpu_handle_halt(CPUState *cpu)
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{
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if (cpu->halted) {
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#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
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if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
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&& replay_interrupt()) {
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X86CPU *x86_cpu = X86_CPU(cpu);
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apic_poll_irq(x86_cpu->apic_state);
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cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
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}
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#endif
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if (!cpu_has_work(cpu)) {
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current_cpu = NULL;
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return true;
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}
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cpu->halted = 0;
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}
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return false;
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}
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static inline void cpu_handle_debug_exception(CPUState *cpu)
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{
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|
CPUClass *cc = CPU_GET_CLASS(cpu);
|
|
CPUWatchpoint *wp;
|
|
|
|
if (!cpu->watchpoint_hit) {
|
|
QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
|
|
wp->flags &= ~BP_WATCHPOINT_HIT;
|
|
}
|
|
}
|
|
|
|
cc->debug_excp_handler(cpu);
|
|
}
|
|
|
|
static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
|
|
{
|
|
if (cpu->exception_index >= 0) {
|
|
if (cpu->exception_index >= EXCP_INTERRUPT) {
|
|
/* exit request from the cpu execution loop */
|
|
*ret = cpu->exception_index;
|
|
if (*ret == EXCP_DEBUG) {
|
|
cpu_handle_debug_exception(cpu);
|
|
}
|
|
cpu->exception_index = -1;
|
|
return true;
|
|
} else {
|
|
#if defined(CONFIG_USER_ONLY)
|
|
/* if user mode only, we simulate a fake exception
|
|
which will be handled outside the cpu execution
|
|
loop */
|
|
#if defined(TARGET_I386)
|
|
CPUClass *cc = CPU_GET_CLASS(cpu);
|
|
cc->do_interrupt(cpu);
|
|
#endif
|
|
*ret = cpu->exception_index;
|
|
cpu->exception_index = -1;
|
|
return true;
|
|
#else
|
|
if (replay_exception()) {
|
|
CPUClass *cc = CPU_GET_CLASS(cpu);
|
|
cc->do_interrupt(cpu);
|
|
cpu->exception_index = -1;
|
|
} else if (!replay_has_interrupt()) {
|
|
/* give a chance to iothread in replay mode */
|
|
*ret = EXCP_INTERRUPT;
|
|
return true;
|
|
}
|
|
#endif
|
|
}
|
|
#ifndef CONFIG_USER_ONLY
|
|
} else if (replay_has_exception()
|
|
&& cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
|
|
/* try to cause an exception pending in the log */
|
|
TranslationBlock *last_tb = NULL; /* Avoid chaining TBs */
|
|
cpu_exec_nocache(cpu, 1, tb_find_fast(cpu, &last_tb, 0), true);
|
|
*ret = -1;
|
|
return true;
|
|
#endif
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static inline void cpu_handle_interrupt(CPUState *cpu,
|
|
TranslationBlock **last_tb)
|
|
{
|
|
CPUClass *cc = CPU_GET_CLASS(cpu);
|
|
int interrupt_request = cpu->interrupt_request;
|
|
|
|
if (unlikely(interrupt_request)) {
|
|
if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
|
|
/* Mask out external interrupts for this step. */
|
|
interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
|
|
}
|
|
if (interrupt_request & CPU_INTERRUPT_DEBUG) {
|
|
cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
|
|
cpu->exception_index = EXCP_DEBUG;
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
|
|
/* Do nothing */
|
|
} else if (interrupt_request & CPU_INTERRUPT_HALT) {
|
|
replay_interrupt();
|
|
cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
|
|
cpu->halted = 1;
|
|
cpu->exception_index = EXCP_HLT;
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
#if defined(TARGET_I386)
|
|
else if (interrupt_request & CPU_INTERRUPT_INIT) {
|
|
X86CPU *x86_cpu = X86_CPU(cpu);
|
|
CPUArchState *env = &x86_cpu->env;
|
|
replay_interrupt();
|
|
cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0);
|
|
do_cpu_init(x86_cpu);
|
|
cpu->exception_index = EXCP_HALTED;
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
#else
|
|
else if (interrupt_request & CPU_INTERRUPT_RESET) {
|
|
replay_interrupt();
|
|
cpu_reset(cpu);
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
#endif
|
|
/* The target hook has 3 exit conditions:
|
|
False when the interrupt isn't processed,
|
|
True when it is, and we should restart on a new TB,
|
|
and via longjmp via cpu_loop_exit. */
|
|
else {
|
|
replay_interrupt();
|
|
if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
|
|
*last_tb = NULL;
|
|
}
|
|
/* The target hook may have updated the 'cpu->interrupt_request';
|
|
* reload the 'interrupt_request' value */
|
|
interrupt_request = cpu->interrupt_request;
|
|
}
|
|
if (interrupt_request & CPU_INTERRUPT_EXITTB) {
|
|
cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
|
|
/* ensure that no TB jump will be modified as
|
|
the program flow was changed */
|
|
*last_tb = NULL;
|
|
}
|
|
}
|
|
if (unlikely(cpu->exit_request || replay_has_interrupt())) {
|
|
cpu->exit_request = 0;
|
|
cpu->exception_index = EXCP_INTERRUPT;
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
}
|
|
|
|
static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
|
|
TranslationBlock **last_tb, int *tb_exit,
|
|
SyncClocks *sc)
|
|
{
|
|
uintptr_t ret;
|
|
|
|
if (unlikely(cpu->exit_request)) {
|
|
return;
|
|
}
|
|
|
|
trace_exec_tb(tb, tb->pc);
|
|
ret = cpu_tb_exec(cpu, tb);
|
|
*last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
|
|
*tb_exit = ret & TB_EXIT_MASK;
|
|
switch (*tb_exit) {
|
|
case TB_EXIT_REQUESTED:
|
|
/* Something asked us to stop executing
|
|
* chained TBs; just continue round the main
|
|
* loop. Whatever requested the exit will also
|
|
* have set something else (eg exit_request or
|
|
* interrupt_request) which we will handle
|
|
* next time around the loop. But we need to
|
|
* ensure the tcg_exit_req read in generated code
|
|
* comes before the next read of cpu->exit_request
|
|
* or cpu->interrupt_request.
|
|
*/
|
|
smp_rmb();
|
|
*last_tb = NULL;
|
|
break;
|
|
case TB_EXIT_ICOUNT_EXPIRED:
|
|
{
|
|
/* Instruction counter expired. */
|
|
#ifdef CONFIG_USER_ONLY
|
|
abort();
|
|
#else
|
|
int insns_left = cpu->icount_decr.u32;
|
|
if (cpu->icount_extra && insns_left >= 0) {
|
|
/* Refill decrementer and continue execution. */
|
|
cpu->icount_extra += insns_left;
|
|
insns_left = MIN(0xffff, cpu->icount_extra);
|
|
cpu->icount_extra -= insns_left;
|
|
cpu->icount_decr.u16.low = insns_left;
|
|
} else {
|
|
if (insns_left > 0) {
|
|
/* Execute remaining instructions. */
|
|
cpu_exec_nocache(cpu, insns_left, *last_tb, false);
|
|
align_clocks(sc, cpu);
|
|
}
|
|
cpu->exception_index = EXCP_INTERRUPT;
|
|
*last_tb = NULL;
|
|
cpu_loop_exit(cpu);
|
|
}
|
|
break;
|
|
#endif
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* main execution loop */
|
|
|
|
int cpu_exec(CPUState *cpu)
|
|
{
|
|
CPUClass *cc = CPU_GET_CLASS(cpu);
|
|
int ret;
|
|
SyncClocks sc;
|
|
|
|
/* replay_interrupt may need current_cpu */
|
|
current_cpu = cpu;
|
|
|
|
if (cpu_handle_halt(cpu)) {
|
|
return EXCP_HALTED;
|
|
}
|
|
|
|
atomic_mb_set(&tcg_current_cpu, cpu);
|
|
rcu_read_lock();
|
|
|
|
if (unlikely(atomic_mb_read(&exit_request))) {
|
|
cpu->exit_request = 1;
|
|
}
|
|
|
|
cc->cpu_exec_enter(cpu);
|
|
|
|
/* Calculate difference between guest clock and host clock.
|
|
* This delay includes the delay of the last cycle, so
|
|
* what we have to do is sleep until it is 0. As for the
|
|
* advance/delay we gain here, we try to fix it next time.
|
|
*/
|
|
init_delay_params(&sc, cpu);
|
|
|
|
for(;;) {
|
|
TranslationBlock *tb, *last_tb;
|
|
int tb_exit = 0;
|
|
|
|
/* prepare setjmp context for exception handling */
|
|
if (sigsetjmp(cpu->jmp_env, 0) == 0) {
|
|
/* if an exception is pending, we execute it here */
|
|
if (cpu_handle_exception(cpu, &ret)) {
|
|
break;
|
|
}
|
|
|
|
last_tb = NULL; /* forget the last executed TB after exception */
|
|
cpu->tb_flushed = false; /* reset before first TB lookup */
|
|
for(;;) {
|
|
cpu_handle_interrupt(cpu, &last_tb);
|
|
tb = tb_find_fast(cpu, &last_tb, tb_exit);
|
|
cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit, &sc);
|
|
/* Try to align the host and virtual clocks
|
|
if the guest is in advance */
|
|
align_clocks(&sc, cpu);
|
|
} /* for(;;) */
|
|
} else {
|
|
#if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
|
|
/* Some compilers wrongly smash all local variables after
|
|
* siglongjmp. There were bug reports for gcc 4.5.0 and clang.
|
|
* Reload essential local variables here for those compilers.
|
|
* Newer versions of gcc would complain about this code (-Wclobbered). */
|
|
cpu = current_cpu;
|
|
cc = CPU_GET_CLASS(cpu);
|
|
#else /* buggy compiler */
|
|
/* Assert that the compiler does not smash local variables. */
|
|
g_assert(cpu == current_cpu);
|
|
g_assert(cc == CPU_GET_CLASS(cpu));
|
|
#endif /* buggy compiler */
|
|
cpu->can_do_io = 1;
|
|
tb_lock_reset();
|
|
}
|
|
} /* for(;;) */
|
|
|
|
cc->cpu_exec_exit(cpu);
|
|
rcu_read_unlock();
|
|
|
|
/* fail safe : never use current_cpu outside cpu_exec() */
|
|
current_cpu = NULL;
|
|
|
|
/* Does not need atomic_mb_set because a spurious wakeup is okay. */
|
|
atomic_set(&tcg_current_cpu, NULL);
|
|
return ret;
|
|
}
|