system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()

The Big QEMU Lock (BQL) has many names and they are confusing. The
actual QemuMutex variable is called qemu_global_mutex but it's commonly
referred to as the BQL in discussions and some code comments. The
locking APIs, however, are called qemu_mutex_lock_iothread() and
qemu_mutex_unlock_iothread().

The "iothread" name is historic and comes from when the main thread was
split into into KVM vcpu threads and the "iothread" (now called the main
loop thread). I have contributed to the confusion myself by introducing
a separate --object iothread, a separate concept unrelated to the BQL.

The "iothread" name is no longer appropriate for the BQL. Rename the
locking APIs to:
- void bql_lock(void)
- void bql_unlock(void)
- bool bql_locked(void)

There are more APIs with "iothread" in their names. Subsequent patches
will rename them. There are also comments and documentation that will be
updated in later patches.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Acked-by: Fabiano Rosas <farosas@suse.de>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Acked-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20240102153529.486531-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

2 files changed, 4 insertions, 4 deletions

diff --git a/target/i386/hvf/README.md b/target/i386/hvf/README.md
index 2d33477aca..64a8935237 100644
--- a/target/i386/hvf/README.md
+++ b/target/i386/hvf/README.md
@@ -4,4 +4,4 @@ These sources (and ../hvf-all.c) are adapted from Veertu Inc's vdhh (Veertu Desk
 
 1. Adapt to our current QEMU's `CPUState` structure and `address_space_rw` API; many struct members have been moved around (emulated x86 state, xsave_buf) due to historical differences + QEMU needing to handle more emulation targets.
 2. Removal of `apic_page` and hyperv-related functionality.
-3. More relaxed use of `qemu_mutex_lock_iothread`.
+3. More relaxed use of `bql_lock`.
diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
index 20b9ca3ef5..11ffdd4c69 100644
--- a/target/i386/hvf/hvf.c
+++ b/target/i386/hvf/hvf.c
@@ -429,9 +429,9 @@ int hvf_vcpu_exec(CPUState *cpu)
         }
         vmx_update_tpr(cpu);
 
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
         if (!cpu_is_bsp(X86_CPU(cpu)) && cpu->halted) {
-            qemu_mutex_lock_iothread();
+            bql_lock();
             return EXCP_HLT;
         }
 
@@ -450,7 +450,7 @@ int hvf_vcpu_exec(CPUState *cpu)
         rip = rreg(cpu->accel->fd, HV_X86_RIP);
         env->eflags = rreg(cpu->accel->fd, HV_X86_RFLAGS);
 
-        qemu_mutex_lock_iothread();
+        bql_lock();
 
         update_apic_tpr(cpu);
         current_cpu = cpu;