KVM: convert bus to slots_lock

Use slots_lock to protect device list on the bus.  slots_lock is already
taken for read everywhere, so we only need to take it for write when
registering devices.  This is in preparation to removing in_range and
kvm->lock around it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

6 files changed, 21 insertions, 7 deletions

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index bcd00c76d69e..4082cdd468ed 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -583,6 +583,7 @@ static const struct kvm_io_device_ops speaker_dev_ops = {
         .in_range = speaker_in_range,
 };
 
+/* Caller must have writers lock on slots_lock */
 struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
 {
         struct kvm_pit *pit;
@@ -621,11 +622,11 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
         kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
 
         kvm_iodevice_init(&pit->dev, &pit_dev_ops);
-        kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
+        __kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
 
         if (flags & KVM_PIT_SPEAKER_DUMMY) {
                 kvm_iodevice_init(&pit->speaker_dev, &speaker_dev_ops);
-                kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
+                __kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
         }
 
         return pit;
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 148c52a608d6..1851aec8a7da 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -548,6 +548,6 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
          * Initialize PIO device
          */
         kvm_iodevice_init(&s->dev, &picdev_ops);
-        kvm_io_bus_register_dev(&kvm->pio_bus, &s->dev);
+        kvm_io_bus_register_dev(kvm, &kvm->pio_bus, &s->dev);
         return s;
 }
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4ea42c950539..96c8c0b01929 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -42,6 +42,7 @@
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID     0
 
+struct kvm;
 struct kvm_vcpu;
 extern struct kmem_cache *kvm_vcpu_cache;
 
@@ -61,7 +62,9 @@ void kvm_io_bus_init(struct kvm_io_bus *bus);
 void kvm_io_bus_destroy(struct kvm_io_bus *bus);
 struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
                                           gpa_t addr, int len, int is_write);
-void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+void __kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+                               struct kvm_io_device *dev);
+void kvm_io_bus_register_dev(struct kvm *kvm, struct kvm_io_bus *bus,
                              struct kvm_io_device *dev);
 
 struct kvm_vcpu {
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index b40946c1237d..7b7cc9fe5ee3 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -102,7 +102,7 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
         kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
         dev->kvm = kvm;
         kvm->coalesced_mmio_dev = dev;
-        kvm_io_bus_register_dev(&kvm->mmio_bus, &dev->dev);
+        kvm_io_bus_register_dev(kvm, &kvm->mmio_bus, &dev->dev);
 
         return 0;
 }
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 0532fa68f5d1..0eca54e06326 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -343,7 +343,7 @@ int kvm_ioapic_init(struct kvm *kvm)
         kvm_ioapic_reset(ioapic);
         kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
         ioapic->kvm = kvm;
-        kvm_io_bus_register_dev(&kvm->mmio_bus, &ioapic->dev);
+        kvm_io_bus_register_dev(kvm, &kvm->mmio_bus, &ioapic->dev);
         return 0;
 }
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bbb4029d7c4d..0edc366ecf89 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2527,7 +2527,17 @@ struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
         return NULL;
 }
 
-void kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)
+void kvm_io_bus_register_dev(struct kvm *kvm, struct kvm_io_bus *bus,
+                             struct kvm_io_device *dev)
+{
+        down_write(&kvm->slots_lock);
+        __kvm_io_bus_register_dev(bus, dev);
+        up_write(&kvm->slots_lock);
+}
+
+/* An unlocked version. Caller must have write lock on slots_lock. */
+void __kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+                             struct kvm_io_device *dev)
 {
         BUG_ON(bus->dev_count > (NR_IOBUS_DEVS-1));