Merge tag 'block-pull-request' of https://gitlab.com/stefanha/qemu into staging

Pull request

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# gpg: Signature made Mon 08 Jan 2024 16:37:25 GMT
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* tag 'block-pull-request' of https://gitlab.com/stefanha/qemu:
  Rename "QEMU global mutex" to "BQL" in comments and docs
  Replace "iothread lock" with "BQL" in comments
  qemu/main-loop: rename qemu_cond_wait_iothread() to qemu_cond_wait_bql()
  qemu/main-loop: rename QEMU_IOTHREAD_LOCK_GUARD to BQL_LOCK_GUARD
  system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()
  iothread: Remove unused Error** argument in aio_context_set_aio_params

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

accel/accel-blocker.c

@@ -41,7 +41,7 @@ void accel_blocker_init(void)
 
 void accel_ioctl_begin(void)
 {
-    if (likely(qemu_mutex_iothread_locked())) {
+    if (likely(bql_locked())) {
         return;
     }
 
@@ -51,7 +51,7 @@ void accel_ioctl_begin(void)
 
 void accel_ioctl_end(void)
 {
-    if (likely(qemu_mutex_iothread_locked())) {
+    if (likely(bql_locked())) {
         return;
     }
 
@@ -62,7 +62,7 @@ void accel_ioctl_end(void)
 
 void accel_cpu_ioctl_begin(CPUState *cpu)
 {
-    if (unlikely(qemu_mutex_iothread_locked())) {
+    if (unlikely(bql_locked())) {
         return;
     }
 
@@ -72,7 +72,7 @@ void accel_cpu_ioctl_begin(CPUState *cpu)
 
 void accel_cpu_ioctl_end(CPUState *cpu)
 {
-    if (unlikely(qemu_mutex_iothread_locked())) {
+    if (unlikely(bql_locked())) {
         return;
     }
 
@@ -105,7 +105,7 @@ void accel_ioctl_inhibit_begin(void)
      * We allow to inhibit only when holding the BQL, so we can identify
      * when an inhibitor wants to issue an ioctl easily.
      */
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
 
     /* Block further invocations of the ioctls outside the BQL.  */
     CPU_FOREACH(cpu) {

accel/dummy-cpus.c

@@ -24,7 +24,7 @@ static void *dummy_cpu_thread_fn(void *arg)
 
     rcu_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
     cpu->neg.can_do_io = true;
@@ -43,7 +43,7 @@ static void *dummy_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
 #ifndef _WIN32
         do {
             int sig;
@@ -56,11 +56,11 @@ static void *dummy_cpu_thread_fn(void *arg)
 #else
         qemu_sem_wait(&cpu->sem);
 #endif
-        qemu_mutex_lock_iothread();
+        bql_lock();
         qemu_wait_io_event(cpu);
     } while (!cpu->unplug);
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     rcu_unregister_thread();
     return NULL;
 }

accel/hvf/hvf-accel-ops.c

@@ -424,7 +424,7 @@ static void *hvf_cpu_thread_fn(void *arg)
 
     rcu_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
 
     cpu->thread_id = qemu_get_thread_id();
@@ -449,7 +449,7 @@ static void *hvf_cpu_thread_fn(void *arg)
 
     hvf_vcpu_destroy(cpu);
     cpu_thread_signal_destroyed(cpu);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     rcu_unregister_thread();
     return NULL;
 }

accel/kvm/kvm-accel-ops.c

@@ -33,7 +33,7 @@ static void *kvm_vcpu_thread_fn(void *arg)
 
     rcu_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
     cpu->neg.can_do_io = true;
@@ -58,7 +58,7 @@ static void *kvm_vcpu_thread_fn(void *arg)
 
     kvm_destroy_vcpu(cpu);
     cpu_thread_signal_destroyed(cpu);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     rcu_unregister_thread();
     return NULL;
 }

accel/kvm/kvm-all.c

@@ -806,7 +806,7 @@ static void kvm_dirty_ring_flush(void)
      * should always be with BQL held, serialization is guaranteed.
      * However, let's be sure of it.
      */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
     /*
      * First make sure to flush the hardware buffers by kicking all
      * vcpus out in a synchronous way.
@@ -1391,9 +1391,9 @@ static void *kvm_dirty_ring_reaper_thread(void *data)
         trace_kvm_dirty_ring_reaper("wakeup");
         r->reaper_state = KVM_DIRTY_RING_REAPER_REAPING;
 
-        qemu_mutex_lock_iothread();
+        bql_lock();
         kvm_dirty_ring_reap(s, NULL);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
 
         r->reaper_iteration++;
     }
@@ -2817,7 +2817,7 @@ int kvm_cpu_exec(CPUState *cpu)
         return EXCP_HLT;
     }
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     cpu_exec_start(cpu);
 
     do {
@@ -2857,11 +2857,11 @@ int kvm_cpu_exec(CPUState *cpu)
 
 #ifdef KVM_HAVE_MCE_INJECTION
         if (unlikely(have_sigbus_pending)) {
-            qemu_mutex_lock_iothread();
+            bql_lock();
             kvm_arch_on_sigbus_vcpu(cpu, pending_sigbus_code,
                                     pending_sigbus_addr);
             have_sigbus_pending = false;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
 #endif
 
@@ -2927,7 +2927,7 @@ int kvm_cpu_exec(CPUState *cpu)
              * still full.  Got kicked by KVM_RESET_DIRTY_RINGS.
              */
             trace_kvm_dirty_ring_full(cpu->cpu_index);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             /*
              * We throttle vCPU by making it sleep once it exit from kernel
              * due to dirty ring full. In the dirtylimit scenario, reaping
@@ -2939,7 +2939,7 @@ int kvm_cpu_exec(CPUState *cpu)
             } else {
                 kvm_dirty_ring_reap(kvm_state, NULL);
             }
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             dirtylimit_vcpu_execute(cpu);
             ret = 0;
             break;
@@ -2956,9 +2956,9 @@ int kvm_cpu_exec(CPUState *cpu)
                 break;
             case KVM_SYSTEM_EVENT_CRASH:
                 kvm_cpu_synchronize_state(cpu);
-                qemu_mutex_lock_iothread();
+                bql_lock();
                 qemu_system_guest_panicked(cpu_get_crash_info(cpu));
-                qemu_mutex_unlock_iothread();
+                bql_unlock();
                 ret = 0;
                 break;
             default:
@@ -2973,7 +2973,7 @@ int kvm_cpu_exec(CPUState *cpu)
     } while (ret == 0);
 
     cpu_exec_end(cpu);
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     if (ret < 0) {
         cpu_dump_state(cpu, stderr, CPU_DUMP_CODE);

accel/tcg/cpu-exec.c

@@ -558,8 +558,8 @@ static void cpu_exec_longjmp_cleanup(CPUState *cpu)
         tcg_ctx->gen_tb = NULL;
     }
 #endif
-    if (qemu_mutex_iothread_locked()) {
-        qemu_mutex_unlock_iothread();
+    if (bql_locked()) {
+        bql_unlock();
     }
     assert_no_pages_locked();
 }
@@ -680,10 +680,10 @@ static inline bool cpu_handle_halt(CPUState *cpu)
 #if defined(TARGET_I386)
         if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
             X86CPU *x86_cpu = X86_CPU(cpu);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             apic_poll_irq(x86_cpu->apic_state);
             cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
 #endif /* TARGET_I386 */
         if (!cpu_has_work(cpu)) {
@@ -749,9 +749,9 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
 #else
         if (replay_exception()) {
             CPUClass *cc = CPU_GET_CLASS(cpu);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             cc->tcg_ops->do_interrupt(cpu);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             cpu->exception_index = -1;
 
             if (unlikely(cpu->singlestep_enabled)) {
@@ -812,7 +812,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
 
     if (unlikely(qatomic_read(&cpu->interrupt_request))) {
         int interrupt_request;
-        qemu_mutex_lock_iothread();
+        bql_lock();
         interrupt_request = cpu->interrupt_request;
         if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
             /* Mask out external interrupts for this step. */
@@ -821,7 +821,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         if (interrupt_request & CPU_INTERRUPT_DEBUG) {
             cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
             cpu->exception_index = EXCP_DEBUG;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #if !defined(CONFIG_USER_ONLY)
@@ -832,7 +832,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
             cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
             cpu->halted = 1;
             cpu->exception_index = EXCP_HLT;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #if defined(TARGET_I386)
@@ -843,14 +843,14 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
             cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
             do_cpu_init(x86_cpu);
             cpu->exception_index = EXCP_HALTED;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #else
         else if (interrupt_request & CPU_INTERRUPT_RESET) {
             replay_interrupt();
             cpu_reset(cpu);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #endif /* !TARGET_I386 */
@@ -873,7 +873,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
                  */
                 if (unlikely(cpu->singlestep_enabled)) {
                     cpu->exception_index = EXCP_DEBUG;
-                    qemu_mutex_unlock_iothread();
+                    bql_unlock();
                     return true;
                 }
                 cpu->exception_index = -1;
@@ -892,7 +892,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         }
 
         /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 
     /* Finally, check if we need to exit to the main loop.  */

accel/tcg/cputlb.c

@@ -1975,7 +1975,7 @@ static void *atomic_mmu_lookup(CPUState *cpu, vaddr addr, MemOpIdx oi,
  * @size: number of bytes
  * @mmu_idx: virtual address context
  * @ra: return address into tcg generated code, or 0
- * Context: iothread lock held
+ * Context: BQL held
  *
  * Load @size bytes from @addr, which is memory-mapped i/o.
  * The bytes are concatenated in big-endian order with @ret_be.
@@ -2030,10 +2030,10 @@ static uint64_t do_ld_mmio_beN(CPUState *cpu, CPUTLBEntryFull *full,
     section = io_prepare(&mr_offset, cpu, full->xlat_section, attrs, addr, ra);
     mr = section->mr;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     ret = int_ld_mmio_beN(cpu, full, ret_be, addr, size, mmu_idx,
                           type, ra, mr, mr_offset);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     return ret;
 }
@@ -2054,12 +2054,12 @@ static Int128 do_ld16_mmio_beN(CPUState *cpu, CPUTLBEntryFull *full,
     section = io_prepare(&mr_offset, cpu, full->xlat_section, attrs, addr, ra);
     mr = section->mr;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     a = int_ld_mmio_beN(cpu, full, ret_be, addr, size - 8, mmu_idx,
                         MMU_DATA_LOAD, ra, mr, mr_offset);
     b = int_ld_mmio_beN(cpu, full, ret_be, addr + size - 8, 8, mmu_idx,
                         MMU_DATA_LOAD, ra, mr, mr_offset + size - 8);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     return int128_make128(b, a);
 }
@@ -2521,7 +2521,7 @@ static Int128 do_ld16_mmu(CPUState *cpu, vaddr addr,
  * @size: number of bytes
  * @mmu_idx: virtual address context
  * @ra: return address into tcg generated code, or 0
- * Context: iothread lock held
+ * Context: BQL held
  *
  * Store @size bytes at @addr, which is memory-mapped i/o.
  * The bytes to store are extracted in little-endian order from @val_le;
@@ -2577,10 +2577,10 @@ static uint64_t do_st_mmio_leN(CPUState *cpu, CPUTLBEntryFull *full,
     section = io_prepare(&mr_offset, cpu, full->xlat_section, attrs, addr, ra);
     mr = section->mr;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     ret = int_st_mmio_leN(cpu, full, val_le, addr, size, mmu_idx,
                           ra, mr, mr_offset);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     return ret;
 }
@@ -2601,12 +2601,12 @@ static uint64_t do_st16_mmio_leN(CPUState *cpu, CPUTLBEntryFull *full,
     section = io_prepare(&mr_offset, cpu, full->xlat_section, attrs, addr, ra);
     mr = section->mr;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     int_st_mmio_leN(cpu, full, int128_getlo(val_le), addr, 8,
                     mmu_idx, ra, mr, mr_offset);
     ret = int_st_mmio_leN(cpu, full, int128_gethi(val_le), addr + 8,
                           size - 8, mmu_idx, ra, mr, mr_offset + 8);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     return ret;
 }

accel/tcg/tcg-accel-ops-icount.c

@@ -123,12 +123,12 @@ void icount_prepare_for_run(CPUState *cpu, int64_t cpu_budget)
 
     if (cpu->icount_budget == 0) {
         /*
-         * We're called without the iothread lock, so must take it while
+         * We're called without the BQL, so must take it while
          * we're calling timer handlers.
          */
-        qemu_mutex_lock_iothread();
+        bql_lock();
         icount_notify_aio_contexts();
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 }
 

accel/tcg/tcg-accel-ops-mttcg.c

@@ -76,7 +76,7 @@ static void *mttcg_cpu_thread_fn(void *arg)
     rcu_add_force_rcu_notifier(&force_rcu.notifier);
     tcg_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
 
     cpu->thread_id = qemu_get_thread_id();
@@ -91,9 +91,9 @@ static void *mttcg_cpu_thread_fn(void *arg)
     do {
         if (cpu_can_run(cpu)) {
             int r;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             r = tcg_cpus_exec(cpu);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             switch (r) {
             case EXCP_DEBUG:
                 cpu_handle_guest_debug(cpu);
@@ -105,9 +105,9 @@ static void *mttcg_cpu_thread_fn(void *arg)
                  */
                 break;
             case EXCP_ATOMIC:
-                qemu_mutex_unlock_iothread();
+                bql_unlock();
                 cpu_exec_step_atomic(cpu);
-                qemu_mutex_lock_iothread();
+                bql_lock();
             default:
                 /* Ignore everything else? */
                 break;
@@ -119,7 +119,7 @@ static void *mttcg_cpu_thread_fn(void *arg)
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     tcg_cpus_destroy(cpu);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     rcu_remove_force_rcu_notifier(&force_rcu.notifier);
     rcu_unregister_thread();
     return NULL;

accel/tcg/tcg-accel-ops-rr.c

@@ -111,7 +111,7 @@ static void rr_wait_io_event(void)
 
     while (all_cpu_threads_idle() && replay_can_wait()) {
         rr_stop_kick_timer();
-        qemu_cond_wait_iothread(first_cpu->halt_cond);
+        qemu_cond_wait_bql(first_cpu->halt_cond);
     }
 
     rr_start_kick_timer();
@@ -188,7 +188,7 @@ static void *rr_cpu_thread_fn(void *arg)
     rcu_add_force_rcu_notifier(&force_rcu);
     tcg_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
 
     cpu->thread_id = qemu_get_thread_id();
@@ -198,7 +198,7 @@ static void *rr_cpu_thread_fn(void *arg)
 
     /* wait for initial kick-off after machine start */
     while (first_cpu->stopped) {
-        qemu_cond_wait_iothread(first_cpu->halt_cond);
+        qemu_cond_wait_bql(first_cpu->halt_cond);
 
         /* process any pending work */
         CPU_FOREACH(cpu) {
@@ -218,9 +218,9 @@ static void *rr_cpu_thread_fn(void *arg)
         /* Only used for icount_enabled() */
         int64_t cpu_budget = 0;
 
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
         replay_mutex_lock();
-        qemu_mutex_lock_iothread();
+        bql_lock();
 
         if (icount_enabled()) {
             int cpu_count = rr_cpu_count();
@@ -254,7 +254,7 @@ static void *rr_cpu_thread_fn(void *arg)
             if (cpu_can_run(cpu)) {
                 int r;
 
-                qemu_mutex_unlock_iothread();
+                bql_unlock();
                 if (icount_enabled()) {
                     icount_prepare_for_run(cpu, cpu_budget);
                 }
@@ -262,15 +262,15 @@ static void *rr_cpu_thread_fn(void *arg)
                 if (icount_enabled()) {
                     icount_process_data(cpu);
                 }
-                qemu_mutex_lock_iothread();
+                bql_lock();
 
                 if (r == EXCP_DEBUG) {
                     cpu_handle_guest_debug(cpu);
                     break;
                 } else if (r == EXCP_ATOMIC) {
-                    qemu_mutex_unlock_iothread();
+                    bql_unlock();
                     cpu_exec_step_atomic(cpu);
-                    qemu_mutex_lock_iothread();
+                    bql_lock();
                     break;
                 }
             } else if (cpu->stop) {

accel/tcg/tcg-accel-ops.c

@@ -88,7 +88,7 @@ static void tcg_cpu_reset_hold(CPUState *cpu)
 /* mask must never be zero, except for A20 change call */
 void tcg_handle_interrupt(CPUState *cpu, int mask)
 {
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
 
     cpu->interrupt_request |= mask;
 

accel/tcg/translate-all.c

@@ -649,7 +649,7 @@ void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
 
 void cpu_interrupt(CPUState *cpu, int mask)
 {
-    g_assert(qemu_mutex_iothread_locked());
+    g_assert(bql_locked());
     cpu->interrupt_request |= mask;
     qatomic_set(&cpu->neg.icount_decr.u16.high, -1);
 }

audio/coreaudio.m

@@ -299,7 +299,7 @@ COREAUDIO_WRAPPER_FUNC(write, size_t, (HWVoiceOut *hw, void *buf, size_t size),
 #undef COREAUDIO_WRAPPER_FUNC
 
 /*
- * callback to feed audiooutput buffer. called without iothread lock.
+ * callback to feed audiooutput buffer. called without BQL.
  * allowed to lock "buf_mutex", but disallowed to have any other locks.
  */
 static OSStatus audioDeviceIOProc(
@@ -538,7 +538,7 @@ static void update_device_playback_state(coreaudioVoiceOut *core)
     }
 }
 
-/* called without iothread lock. */
+/* called without BQL. */
 static OSStatus handle_voice_change(
     AudioObjectID in_object_id,
     UInt32 in_number_addresses,
@@ -547,7 +547,7 @@ static OSStatus handle_voice_change(
 {
     coreaudioVoiceOut *core = in_client_data;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     if (core->outputDeviceID) {
         fini_out_device(core);
@@ -557,7 +557,7 @@ static OSStatus handle_voice_change(
         update_device_playback_state(core);
     }
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     return 0;
 }
 

cpu-common.c

@@ -351,11 +351,11 @@ void process_queued_cpu_work(CPUState *cpu)
              * BQL, so it goes to sleep; start_exclusive() is sleeping too, so
              * neither CPU can proceed.
              */
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             start_exclusive();
             wi->func(cpu, wi->data);
             end_exclusive();
-            qemu_mutex_lock_iothread();
+            bql_lock();
         } else {
             wi->func(cpu, wi->data);
         }

docs/devel/multi-thread-tcg.rst

@@ -226,10 +226,9 @@ instruction. This could be a future optimisation.
 Emulated hardware state
 -----------------------
 
-Currently thanks to KVM work any access to IO memory is automatically
-protected by the global iothread mutex, also known as the BQL (Big
-QEMU Lock). Any IO region that doesn't use global mutex is expected to
-do its own locking.
+Currently thanks to KVM work any access to IO memory is automatically protected
+by the BQL (Big QEMU Lock). Any IO region that doesn't use the BQL is expected
+to do its own locking.
 
 However IO memory isn't the only way emulated hardware state can be
 modified. Some architectures have model specific registers that

docs/devel/multiple-iothreads.txt

@@ -5,7 +5,7 @@ the COPYING file in the top-level directory.
 
 
 This document explains the IOThread feature and how to write code that runs
-outside the QEMU global mutex.
+outside the BQL.
 
 The main loop and IOThreads
 ---------------------------
@@ -29,13 +29,13 @@ scalability bottleneck on hosts with many CPUs.  Work can be spread across
 several IOThreads instead of just one main loop.  When set up correctly this
 can improve I/O latency and reduce jitter seen by the guest.
 
-The main loop is also deeply associated with the QEMU global mutex, which is a
-scalability bottleneck in itself.  vCPU threads and the main loop use the QEMU
-global mutex to serialize execution of QEMU code.  This mutex is necessary
-because a lot of QEMU's code historically was not thread-safe.
+The main loop is also deeply associated with the BQL, which is a
+scalability bottleneck in itself.  vCPU threads and the main loop use the BQL
+to serialize execution of QEMU code.  This mutex is necessary because a lot of
+QEMU's code historically was not thread-safe.
 
 The fact that all I/O processing is done in a single main loop and that the
-QEMU global mutex is contended by all vCPU threads and the main loop explain
+BQL is contended by all vCPU threads and the main loop explain
 why it is desirable to place work into IOThreads.
 
 The experimental virtio-blk data-plane implementation has been benchmarked and
@@ -66,7 +66,7 @@ There are several old APIs that use the main loop AioContext:
 
 Since they implicitly work on the main loop they cannot be used in code that
 runs in an IOThread.  They might cause a crash or deadlock if called from an
-IOThread since the QEMU global mutex is not held.
+IOThread since the BQL is not held.
 
 Instead, use the AioContext functions directly (see include/block/aio.h):
  * aio_set_fd_handler() - monitor a file descriptor

docs/devel/qapi-code-gen.rst

@@ -594,7 +594,7 @@ blocking the guest and other background operations.
 Coroutine safety can be hard to prove, similar to thread safety.  Common
 pitfalls are:
 
-- The global mutex isn't held across ``qemu_coroutine_yield()``, so
+- The BQL isn't held across ``qemu_coroutine_yield()``, so
   operations that used to assume that they execute atomically may have
   to be more careful to protect against changes in the global state.
 

docs/devel/replay.rst

@@ -184,7 +184,7 @@ modes.
 Reading and writing requests are created by CPU thread of QEMU. Later these
 requests proceed to block layer which creates "bottom halves". Bottom
 halves consist of callback and its parameters. They are processed when
-main loop locks the global mutex. These locks are not synchronized with
+main loop locks the BQL. These locks are not synchronized with
 replaying process because main loop also processes the events that do not
 affect the virtual machine state (like user interaction with monitor).
 

docs/devel/reset.rst

@@ -19,7 +19,7 @@ Triggering reset
 
 This section documents the APIs which "users" of a resettable object should use
 to control it. All resettable control functions must be called while holding
-the iothread lock.
+the BQL.
 
 You can apply a reset to an object using ``resettable_assert_reset()``. You need
 to call ``resettable_release_reset()`` to release the object from reset. To

dump/dump.c

@@ -108,11 +108,11 @@ static int dump_cleanup(DumpState *s)
     s->guest_note = NULL;
     if (s->resume) {
         if (s->detached) {
-            qemu_mutex_lock_iothread();
+            bql_lock();
         }
         vm_start();
         if (s->detached) {
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
     }
     migrate_del_blocker(&dump_migration_blocker);