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tcg: remove global exit_request

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There are now only two uses of the global exit_request left.

The first ensures we exit the run_loop when we first start to process
pending work and in the kick handler. This is just as easily done by
setting the first_cpu->exit_request flag.

The second use is in the round robin kick routine. The global
exit_request ensured every vCPU would set its local exit_request and
cause a full exit of the loop. Now the iothread isn't being held while
running we can just rely on the kick handler to push us out as intended.

We lightly re-factor the main vCPU thread to ensure cpu->exit_requests
cause us to exit the main loop and process any IO requests that might
come along. As an cpu->exit_request may legitimately get squashed
while processing the EXCP_INTERRUPT exception we also check
cpu->queued_work_first to ensure queued work is expedited as soon as
possible.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Alex Bennée 2017-02-23 18:29:12 +00:00
parent 8d04fb55de
commit e5143e30fb
4 changed files with 18 additions and 26 deletions
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20
cpu-exec.c
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@ -568,15 +568,13 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
*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 zeroing of tcg_exit_req (see cpu_tb_exec)
* comes before the next read of cpu->exit_request
* or cpu->interrupt_request.
/* 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 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_mb();
*last_tb = NULL;
@ -630,10 +628,6 @@ int cpu_exec(CPUState *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.