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tcg: handle EXCP_ATOMIC exception for system emulation

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The patch enables handling atomic code in the guest. This should be
preferably done in cpu_handle_exception(), but the current assumptions
regarding when we can execute atomic sections cause a deadlock.

The current mechanism discards the flags which were set in atomic
execution. We ensure they are properly saved by calling the
cc->cpu_exec_enter/leave() functions around the loop.

As we are running cpu_exec_step_atomic() from the outermost loop we
need to avoid an abort() when single stepping over atomic code since
debug exception longjmp will point to the the setlongjmp in
cpu_exec(). We do this by setting a new jmp_env so that it jumps back
here on an exception.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
[AJB: tweak title, merge with new patches, add mmap_lock]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
CC: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Pranith Kumar 2017-02-23 18:29:15 +00:00 committed by Alex Bennée
parent 372579427a
commit 08e73c48b0
2 changed files with 40 additions and 12 deletions
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43
cpu-exec.c
View file

@ -228,24 +228,43 @@ static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
static void cpu_exec_step(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
CPUArchState *env = (CPUArchState *)cpu->env_ptr;
TranslationBlock *tb;
target_ulong cs_base, pc;
uint32_t flags;
cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
tb_lock();
tb = tb_gen_code(cpu, pc, cs_base, flags,
1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
tb->orig_tb = NULL;
tb_unlock();
/* execute the generated code */
trace_exec_tb_nocache(tb, pc);
cpu_tb_exec(cpu, tb);
tb_lock();
tb_phys_invalidate(tb, -1);
tb_free(tb);
tb_unlock();
if (sigsetjmp(cpu->jmp_env, 0) == 0) {
mmap_lock();
tb_lock();
tb = tb_gen_code(cpu, pc, cs_base, flags,
1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
tb->orig_tb = NULL;
tb_unlock();
mmap_unlock();
cc->cpu_exec_enter(cpu);
/* execute the generated code */
trace_exec_tb_nocache(tb, pc);
cpu_tb_exec(cpu, tb);
cc->cpu_exec_exit(cpu);
tb_lock();
tb_phys_invalidate(tb, -1);
tb_free(tb);
tb_unlock();
} else {
/* We may have exited due to another problem here, so we need
* to reset any tb_locks we may have taken but didn't release.
* The mmap_lock is dropped by tb_gen_code if it runs out of
* memory.
*/
#ifndef CONFIG_SOFTMMU
tcg_debug_assert(!have_mmap_lock());
#endif
tb_lock_reset();
}
}
void cpu_exec_step_atomic(CPUState *cpu)

9
cpus.c
View file

@ -1348,6 +1348,11 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
if (r == EXCP_DEBUG) {
cpu_handle_guest_debug(cpu);
break;
} else if (r == EXCP_ATOMIC) {
qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
qemu_mutex_lock_iothread();
break;
}
} else if (cpu->stop) {
if (cpu->unplug) {
@ -1458,6 +1463,10 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
*/
g_assert(cpu->halted);
break;
case EXCP_ATOMIC:
qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
qemu_mutex_lock_iothread();
default:
/* Ignore everything else? */
break;