[KVM PATCH v2 3/4] kvm: add io_bus unregister function

[Gregory Haskins]

We want to support the notion of dynamic MMIO/PIO registrations and
therefore will need to support both register as well as unregister.

However, the current io_bus code is structured as a linear array and
is not conducive to unregistering, so refactor to allow "holes" in the
array.  We then enhance the API with an unregister function.

Signed-off-by: Gregory Haskins <ghask...@novell.com>
---

 include/linux/kvm_host.h |    4 +++-
 virt/kvm/kvm_main.c      |   48 ++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 94c1a11..214089f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -52,7 +52,7 @@ extern struct kmem_cache *kvm_vcpu_cache;
  * in one place.
  */
 struct kvm_io_bus {
-       int                   dev_count;
+       spinlock_t lock;
 #define NR_IOBUS_DEVS 6
        struct kvm_io_device *devs[NR_IOBUS_DEVS];
 };
@@ -63,6 +63,8 @@ struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus 
*bus,
                                          gpa_t addr, int len, int is_write);
 int kvm_io_bus_register_dev(struct kvm_io_bus *bus,
                            struct kvm_io_device *dev);
+int kvm_io_bus_unregister_dev(struct kvm_io_bus *bus,
+                           struct kvm_io_device *dev);
 
 struct kvm_vcpu {
        struct kvm *kvm;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 60ba0cf..5f5e443 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2433,16 +2433,18 @@ static struct notifier_block kvm_reboot_notifier = {
 void kvm_io_bus_init(struct kvm_io_bus *bus)
 {
        memset(bus, 0, sizeof(*bus));
+       spin_lock_init(&bus->lock);
 }
 
 void kvm_io_bus_destroy(struct kvm_io_bus *bus)
 {
        int i;
 
-       for (i = 0; i < bus->dev_count; i++) {
+       for (i = 0; i < NR_IOBUS_DEVS; i++) {
                struct kvm_io_device *pos = bus->devs[i];
 
-               kvm_iodevice_destructor(pos);
+               if (pos)
+                       kvm_iodevice_destructor(pos);
        }
 }
 
@@ -2451,10 +2453,10 @@ struct kvm_io_device *kvm_io_bus_find_dev(struct 
kvm_io_bus *bus,
 {
        int i;
 
-       for (i = 0; i < bus->dev_count; i++) {
+       for (i = 0; i < NR_IOBUS_DEVS; i++) {
                struct kvm_io_device *pos = bus->devs[i];
 
-               if (pos->in_range(pos, addr, len, is_write))
+               if (pos && pos->in_range(pos, addr, len, is_write))
                        return pos;
        }
 
@@ -2463,12 +2465,42 @@ struct kvm_io_device *kvm_io_bus_find_dev(struct 
kvm_io_bus *bus,
 
 int kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)
 {
-       if (bus->dev_count > (NR_IOBUS_DEVS-1))
-               return -ENOSPC;
+       int i;
 
-       bus->devs[bus->dev_count++] = dev;
+       spin_lock(&bus->lock);
 
-       return 0;
+       for (i = 0; i < NR_IOBUS_DEVS; i++) {
+               if (bus->devs[i])
+                       continue;
+
+               bus->devs[i] = dev;
+               spin_unlock(&bus->lock);
+               return 0;
+       }
+
+       spin_unlock(&bus->lock);
+
+       return -ENOSPC;
+}
+
+int kvm_io_bus_unregister_dev(struct kvm_io_bus *bus, struct kvm_io_device 
*dev)
+{
+       int i;
+
+       spin_lock(&bus->lock);
+
+       for (i = 0; i < NR_IOBUS_DEVS; i++) {
+
+               if (bus->devs[i] == dev) {
+                       bus->devs[i] = NULL;
+                       spin_unlock(&bus->lock);
+                       return 0;
+               }
+       }
+
+       spin_unlock(&bus->lock);
+
+       return -ENOENT;
 }
 
 static struct notifier_block kvm_cpu_notifier = {

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