tcg: remove global exit_request

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>

1 files changed, 7 insertions, 13 deletions

diff --git a/cpu-exec.c b/cpu-exec.c
index 1bd3d72002..85f14d4194 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -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.