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>

4 files changed, 13 insertions, 13 deletions

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index ed5677c0ae..1a07faddb4 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1665,7 +1665,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
 {
     bool use_iommu, pt;
     /* Whether we need to take the BQL on our own */
-    bool take_bql = !qemu_mutex_iothread_locked();
+    bool take_bql = !bql_locked();
 
     assert(as);
 
@@ -1683,7 +1683,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
      * it. We'd better make sure we have had it already, or, take it.
      */
     if (take_bql) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
 
     /* Turn off first then on the other */
@@ -1738,7 +1738,7 @@ static bool vtd_switch_address_space(VTDAddressSpace *as)
     }
 
     if (take_bql) {
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 
     return use_iommu;
diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
index 9a5f3caa24..4a835a1010 100644
--- a/hw/i386/kvm/xen_evtchn.c
+++ b/hw/i386/kvm/xen_evtchn.c
@@ -425,7 +425,7 @@ void xen_evtchn_set_callback_level(int level)
      * effect immediately. That just leaves interdomain loopback as the case
      * which uses the BH.
      */
-    if (!qemu_mutex_iothread_locked()) {
+    if (!bql_locked()) {
         qemu_bh_schedule(s->gsi_bh);
         return;
     }
@@ -459,7 +459,7 @@ int xen_evtchn_set_callback_param(uint64_t param)
      * We need the BQL because set_callback_pci_intx() may call into PCI code,
      * and because we may need to manipulate the old and new GSI levels.
      */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
     qemu_mutex_lock(&s->port_lock);
 
     switch (type) {
@@ -1037,7 +1037,7 @@ static int close_port(XenEvtchnState *s, evtchn_port_t port,
     XenEvtchnPort *p = &s->port_table[port];
 
     /* Because it *might* be a PIRQ port */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     switch (p->type) {
     case EVTCHNSTAT_closed:
@@ -1104,7 +1104,7 @@ int xen_evtchn_soft_reset(void)
         return -ENOTSUP;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     qemu_mutex_lock(&s->port_lock);
 
@@ -1601,7 +1601,7 @@ bool xen_evtchn_set_gsi(int gsi, int level)
     XenEvtchnState *s = xen_evtchn_singleton;
     int pirq;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (!s || gsi < 0 || gsi >= IOAPIC_NUM_PINS) {
         return false;
@@ -1712,7 +1712,7 @@ void xen_evtchn_snoop_msi(PCIDevice *dev, bool is_msix, unsigned int vector,
         return;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(addr, data);
 
@@ -1749,7 +1749,7 @@ int xen_evtchn_translate_pirq_msi(struct kvm_irq_routing_entry *route,
         return 1; /* Not a PIRQ */
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(address, data);
     if (!pirq || pirq >= s->nr_pirqs) {
@@ -1796,7 +1796,7 @@ bool xen_evtchn_deliver_pirq_msi(uint64_t address, uint32_t data)
         return false;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     pirq = msi_pirq_target(address, data);
     if (!pirq || pirq >= s->nr_pirqs) {
diff --git a/hw/i386/kvm/xen_overlay.c b/hw/i386/kvm/xen_overlay.c
index 526f7a6077..c68e78ac5c 100644
--- a/hw/i386/kvm/xen_overlay.c
+++ b/hw/i386/kvm/xen_overlay.c
@@ -194,7 +194,7 @@ int xen_overlay_map_shinfo_page(uint64_t gpa)
         return -ENOENT;
     }
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     if (s->shinfo_gpa) {
         /* If removing shinfo page, turn the kernel magic off first */
diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
index c3633f7829..1a9bc342b8 100644
--- a/hw/i386/kvm/xen_xenstore.c
+++ b/hw/i386/kvm/xen_xenstore.c
@@ -1341,7 +1341,7 @@ static void fire_watch_cb(void *opaque, const char *path, const char *token)
 {
     XenXenstoreState *s = opaque;
 
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
 
     /*
      * If there's a response pending, we obviously can't scribble over