[PATCH 17/18] accel: make all calls to qemu_wait_io_event look the same

[Paolo Bonzini <pbonzini@redhat.com>]

There is no reason for some accelerators to use qemu_wait_io_event_common
(which is separated from qemu_wait_io_event() specifically for round
robin).  They can also check for events directly on the first pass through
the loop, instead of setting cpu->exit_request to true.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 accel/dummy-cpus.c                |  2 +-
 accel/hvf/hvf-accel-ops.c         |  2 +-
 accel/kvm/kvm-accel-ops.c         |  3 ++-
 accel/tcg/tcg-accel-ops-mttcg.c   |  7 ++---
 accel/tcg/tcg-accel-ops-rr.c      | 43 ++++++++++++++-----------------
 target/i386/nvmm/nvmm-accel-ops.c |  6 ++---
 target/i386/whpx/whpx-accel-ops.c |  6 ++---
 7 files changed, 30 insertions(+), 39 deletions(-)

diff --git a/accel/dummy-cpus.c b/accel/dummy-cpus.c
index 03cfc0fa01e..1f74c727c42 100644
--- a/accel/dummy-cpus.c
+++ b/accel/dummy-cpus.c
@@ -43,6 +43,7 @@ static void *dummy_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
+        qemu_wait_io_event(cpu);
         bql_unlock();
 #ifndef _WIN32
         do {
@@ -57,7 +58,6 @@ static void *dummy_cpu_thread_fn(void *arg)
         qemu_sem_wait(&cpu->sem);
 #endif
         bql_lock();
-        qemu_wait_io_event(cpu);
     } while (!cpu->unplug);
 
     bql_unlock();
diff --git a/accel/hvf/hvf-accel-ops.c b/accel/hvf/hvf-accel-ops.c
index d488d6afbac..4ba3e40831f 100644
--- a/accel/hvf/hvf-accel-ops.c
+++ b/accel/hvf/hvf-accel-ops.c
@@ -192,13 +192,13 @@ static void *hvf_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
+        qemu_wait_io_event(cpu);
         if (cpu_can_run(cpu)) {
             r = hvf_vcpu_exec(cpu);
             if (r == EXCP_DEBUG) {
                 cpu_handle_guest_debug(cpu);
             }
         }
-        qemu_wait_io_event(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     hvf_vcpu_destroy(cpu);
diff --git a/accel/kvm/kvm-accel-ops.c b/accel/kvm/kvm-accel-ops.c
index b709187c7d7..80f0141a8a6 100644
--- a/accel/kvm/kvm-accel-ops.c
+++ b/accel/kvm/kvm-accel-ops.c
@@ -47,13 +47,14 @@ static void *kvm_vcpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
+        qemu_wait_io_event(cpu);
+
         if (cpu_can_run(cpu)) {
             r = kvm_cpu_exec(cpu);
             if (r == EXCP_DEBUG) {
                 cpu_handle_guest_debug(cpu);
             }
         }
-        qemu_wait_io_event(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     kvm_destroy_vcpu(cpu);
diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
index 1148ebcaae5..04012900a30 100644
--- a/accel/tcg/tcg-accel-ops-mttcg.c
+++ b/accel/tcg/tcg-accel-ops-mttcg.c
@@ -84,10 +84,9 @@ static void *mttcg_cpu_thread_fn(void *arg)
     cpu_thread_signal_created(cpu);
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
-    /* process any pending work */
-    qatomic_set(&cpu->exit_request, true);
-
     do {
+        qemu_wait_io_event(cpu);
+
         if (cpu_can_run(cpu)) {
             int r;
             bql_unlock();
@@ -112,8 +111,6 @@ static void *mttcg_cpu_thread_fn(void *arg)
                 break;
             }
         }
-
-        qemu_wait_io_event(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     tcg_cpu_destroy(cpu);
diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c
index e9d291dc391..28897288db7 100644
--- a/accel/tcg/tcg-accel-ops-rr.c
+++ b/accel/tcg/tcg-accel-ops-rr.c
@@ -211,13 +211,30 @@ static void *rr_cpu_thread_fn(void *arg)
 
     cpu = first_cpu;
 
-    /* process any pending work */
-    qatomic_set(&cpu->exit_request, true);
-
     while (1) {
         /* Only used for icount_enabled() */
         int64_t cpu_budget = 0;
 
+        if (cpu) {
+            /*
+             * This could even reset exit_request for all CPUs, but in practice
+             * races between CPU exits and changes to "cpu" are so rare that
+             * there's no advantage in doing so.
+             */
+            qatomic_set(&cpu->exit_request, false);
+        }
+
+        if (icount_enabled() && all_cpu_threads_idle()) {
+            /*
+             * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
+             * in the main_loop, wake it up in order to start the warp timer.
+             */
+            qemu_notify_event();
+        }
+
+        rr_wait_io_event();
+        rr_deal_with_unplugged_cpus();
+
         bql_unlock();
         replay_mutex_lock();
         bql_lock();
@@ -285,26 +302,6 @@ static void *rr_cpu_thread_fn(void *arg)
 
         /* Does not need a memory barrier because a spurious wakeup is okay.  */
         qatomic_set(&rr_current_cpu, NULL);
-
-        if (cpu) {
-            /*
-             * This could even reset exit_request for all CPUs, but in practice
-             * races between CPU exits and changes to "cpu" are so rare that
-             * there's no advantage in doing so.
-             */
-            qatomic_set(&cpu->exit_request, false);
-        }
-
-        if (icount_enabled() && all_cpu_threads_idle()) {
-            /*
-             * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
-             * in the main_loop, wake it up in order to start the warp timer.
-             */
-            qemu_notify_event();
-        }
-
-        rr_wait_io_event();
-        rr_deal_with_unplugged_cpus();
     }
 
     g_assert_not_reached();
diff --git a/target/i386/nvmm/nvmm-accel-ops.c b/target/i386/nvmm/nvmm-accel-ops.c
index 86869f133e9..f51244740d8 100644
--- a/target/i386/nvmm/nvmm-accel-ops.c
+++ b/target/i386/nvmm/nvmm-accel-ops.c
@@ -42,16 +42,14 @@ static void *qemu_nvmm_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
+        qemu_wait_io_event(cpu);
+
         if (cpu_can_run(cpu)) {
             r = nvmm_vcpu_exec(cpu);
             if (r == EXCP_DEBUG) {
                 cpu_handle_guest_debug(cpu);
             }
         }
-        while (cpu_thread_is_idle(cpu)) {
-            qemu_cond_wait_bql(cpu->halt_cond);
-        }
-        qemu_wait_io_event_common(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     nvmm_destroy_vcpu(cpu);
diff --git a/target/i386/whpx/whpx-accel-ops.c b/target/i386/whpx/whpx-accel-ops.c
index da58805b1a6..611eeedeef7 100644
--- a/target/i386/whpx/whpx-accel-ops.c
+++ b/target/i386/whpx/whpx-accel-ops.c
@@ -42,16 +42,14 @@ static void *whpx_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
+        qemu_wait_io_event(cpu);
+
         if (cpu_can_run(cpu)) {
             r = whpx_vcpu_exec(cpu);
             if (r == EXCP_DEBUG) {
                 cpu_handle_guest_debug(cpu);
             }
         }
-        while (cpu_thread_is_idle(cpu)) {
-            qemu_cond_wait_bql(cpu->halt_cond);
-        }
-        qemu_wait_io_event_common(cpu);
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     whpx_destroy_vcpu(cpu);
-- 
2.51.0