4 files changed, 56 insertions, 8 deletions

diff --git a/accel/tcg/tcg-accel-ops-icount.c b/accel/tcg/tcg-accel-ops-icount.c
index 84cc7421be..3d2cfbbc97 100644
--- a/accel/tcg/tcg-accel-ops-icount.c
+++ b/accel/tcg/tcg-accel-ops-icount.c
@@ -89,7 +89,20 @@ void icount_handle_deadline(void)
     }
 }
 
-void icount_prepare_for_run(CPUState *cpu)
+/* Distribute the budget evenly across all CPUs */
+int64_t icount_percpu_budget(int cpu_count)
+{
+    int64_t limit = icount_get_limit();
+    int64_t timeslice = limit / cpu_count;
+
+    if (timeslice == 0) {
+        timeslice = limit;
+    }
+
+    return timeslice;
+}
+
+void icount_prepare_for_run(CPUState *cpu, int64_t cpu_budget)
 {
     int insns_left;
 
@@ -101,13 +114,13 @@ void icount_prepare_for_run(CPUState *cpu)
     g_assert(cpu_neg(cpu)->icount_decr.u16.low == 0);
     g_assert(cpu->icount_extra == 0);
 
-    cpu->icount_budget = icount_get_limit();
+    replay_mutex_lock();
+
+    cpu->icount_budget = MIN(icount_get_limit(), cpu_budget);
     insns_left = MIN(0xffff, cpu->icount_budget);
     cpu_neg(cpu)->icount_decr.u16.low = insns_left;
     cpu->icount_extra = cpu->icount_budget - insns_left;
 
-    replay_mutex_lock();
-
     if (cpu->icount_budget == 0) {
         /*
          * We're called without the iothread lock, so must take it while
diff --git a/accel/tcg/tcg-accel-ops-icount.h b/accel/tcg/tcg-accel-ops-icount.h
index 1b6fd9c607..16a301b6dc 100644
--- a/accel/tcg/tcg-accel-ops-icount.h
+++ b/accel/tcg/tcg-accel-ops-icount.h
@@ -11,7 +11,8 @@
 #define TCG_ACCEL_OPS_ICOUNT_H
 
 void icount_handle_deadline(void);
-void icount_prepare_for_run(CPUState *cpu);
+void icount_prepare_for_run(CPUState *cpu, int64_t cpu_budget);
+int64_t icount_percpu_budget(int cpu_count);
 void icount_process_data(CPUState *cpu);
 
 void icount_handle_interrupt(CPUState *cpu, int mask);
diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c
index 290833a37f..5788efa5ff 100644
--- a/accel/tcg/tcg-accel-ops-rr.c
+++ b/accel/tcg/tcg-accel-ops-rr.c
@@ -24,6 +24,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/lockable.h"
 #include "sysemu/tcg.h"
 #include "sysemu/replay.h"
 #include "sysemu/cpu-timers.h"
@@ -140,6 +141,33 @@ static void rr_force_rcu(Notifier *notify, void *data)
 }
 
 /*
+ * Calculate the number of CPUs that we will process in a single iteration of
+ * the main CPU thread loop so that we can fairly distribute the instruction
+ * count across CPUs.
+ *
+ * The CPU count is cached based on the CPU list generation ID to avoid
+ * iterating the list every time.
+ */
+static int rr_cpu_count(void)
+{
+    static unsigned int last_gen_id = ~0;
+    static int cpu_count;
+    CPUState *cpu;
+
+    QEMU_LOCK_GUARD(&qemu_cpu_list_lock);
+
+    if (cpu_list_generation_id_get() != last_gen_id) {
+        cpu_count = 0;
+        CPU_FOREACH(cpu) {
+            ++cpu_count;
+        }
+        last_gen_id = cpu_list_generation_id_get();
+    }
+
+    return cpu_count;
+}
+
+/*
  * In the single-threaded case each vCPU is simulated in turn. If
  * there is more than a single vCPU we create a simple timer to kick
  * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
@@ -185,11 +213,16 @@ static void *rr_cpu_thread_fn(void *arg)
     cpu->exit_request = 1;
 
     while (1) {
+        /* Only used for icount_enabled() */
+        int64_t cpu_budget = 0;
+
         qemu_mutex_unlock_iothread();
         replay_mutex_lock();
         qemu_mutex_lock_iothread();
 
         if (icount_enabled()) {
+            int cpu_count = rr_cpu_count();
+
             /* Account partial waits to QEMU_CLOCK_VIRTUAL.  */
             icount_account_warp_timer();
             /*
@@ -197,6 +230,8 @@ static void *rr_cpu_thread_fn(void *arg)
              * waking up the I/O thread and waiting for completion.
              */
             icount_handle_deadline();
+
+            cpu_budget = icount_percpu_budget(cpu_count);
         }
 
         replay_mutex_unlock();
@@ -218,7 +253,7 @@ static void *rr_cpu_thread_fn(void *arg)
 
                 qemu_mutex_unlock_iothread();
                 if (icount_enabled()) {
-                    icount_prepare_for_run(cpu);
+                    icount_prepare_for_run(cpu, cpu_budget);
                 }
                 r = tcg_cpus_exec(cpu);
                 if (icount_enabled()) {
diff --git a/replay/replay.c b/replay/replay.c
index c39156c522..0f7d766efe 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -74,7 +74,7 @@ uint64_t replay_get_current_icount(void)
 int replay_get_instructions(void)
 {
     int res = 0;
-    replay_mutex_lock();
+    g_assert(replay_mutex_locked());
     if (replay_next_event_is(EVENT_INSTRUCTION)) {
         res = replay_state.instruction_count;
         if (replay_break_icount != -1LL) {
@@ -85,7 +85,6 @@ int replay_get_instructions(void)
             }
         }
     }
-    replay_mutex_unlock();
     return res;
 }