Re: [PATCH v4 04/25] virtio: defer config changed notifications
On Tue, Oct 14, 2014 at 11:01:12AM +1030, Rusty Russell wrote:
> "Michael S. Tsirkin" writes:
> > Defer config changed notifications that arrive during
> > probe/scan/freeze/restore.
> >
> > This will allow drivers to set DRIVER_OK earlier, without worrying about
> > racing with config change interrupts.
> >
> > This change will also benefit old hypervisors (before 2009)
> > that send interrupts without checking DRIVER_OK: previously,
> > the callback could race with driver-specific initialization.
> >
> > This will also help simplify drivers.
>
> But AFAICT you never *read* dev->config_changed.
>
> You unconditionally trigger a config_changed event in
> virtio_config_enable(). That's a bit weird, but probably OK.
>
> How about the following change (on top of your patch). I
> think the renaming is clearer, and note the added if() test in
> virtio_config_enable().
>
> If you approve, I'll fold it in.
>
> Cheers,
> Rusty.
Hi Rusty,
I'm okay with both changes.
You can fold it in if you prefer, or just make it a patch on top.
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 2536701b098b..df598dd8c5c8 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -122,7 +122,7 @@ static void __virtio_config_changed(struct virtio_device
> *dev)
> struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
>
> if (!dev->config_enabled)
> - dev->config_changed = true;
> + dev->config_change_pending = true;
> else if (drv && drv->config_changed)
> drv->config_changed(dev);
> }
> @@ -148,8 +148,9 @@ static void virtio_config_enable(struct virtio_device
> *dev)
> {
> spin_lock_irq(&dev->config_lock);
> dev->config_enabled = true;
> - __virtio_config_changed(dev);
> - dev->config_changed = false;
> + if (dev->config_change_pending)
> + __virtio_config_changed(dev);
> + dev->config_change_pending = false;
> spin_unlock_irq(&dev->config_lock);
> }
>
> @@ -253,7 +254,7 @@ int register_virtio_device(struct virtio_device *dev)
>
> spin_lock_init(&dev->config_lock);
> dev->config_enabled = false;
> - dev->config_changed = false;
> + dev->config_change_pending = false;
>
> /* We always start by resetting the device, in case a previous
>* driver messed it up. This also tests that code path a little. */
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 5636b119dc25..65261a7244fc 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -80,7 +80,7 @@ bool virtqueue_is_broken(struct virtqueue *vq);
> * @index: unique position on the virtio bus
> * @failed: saved value for CONFIG_S_FAILED bit (for restore)
> * @config_enabled: configuration change reporting enabled
> - * @config_changed: configuration change reported while disabled
> + * @config_change_pending: configuration change reported while disabled
> * @config_lock: protects configuration change reporting
> * @dev: underlying device.
> * @id: the device type identification (used to match it with a driver).
> @@ -94,7 +94,7 @@ struct virtio_device {
> int index;
> bool failed;
> bool config_enabled;
> - bool config_changed;
> + bool config_change_pending;
> spinlock_t config_lock;
> struct device dev;
> struct virtio_device_id id;
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Re: [PATCH v4 04/25] virtio: defer config changed notifications
"Michael S. Tsirkin" writes:
> Defer config changed notifications that arrive during
> probe/scan/freeze/restore.
>
> This will allow drivers to set DRIVER_OK earlier, without worrying about
> racing with config change interrupts.
>
> This change will also benefit old hypervisors (before 2009)
> that send interrupts without checking DRIVER_OK: previously,
> the callback could race with driver-specific initialization.
>
> This will also help simplify drivers.
But AFAICT you never *read* dev->config_changed.
You unconditionally trigger a config_changed event in
virtio_config_enable(). That's a bit weird, but probably OK.
How about the following change (on top of your patch). I
think the renaming is clearer, and note the added if() test in
virtio_config_enable().
If you approve, I'll fold it in.
Cheers,
Rusty.
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 2536701b098b..df598dd8c5c8 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -122,7 +122,7 @@ static void __virtio_config_changed(struct virtio_device
*dev)
struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
if (!dev->config_enabled)
- dev->config_changed = true;
+ dev->config_change_pending = true;
else if (drv && drv->config_changed)
drv->config_changed(dev);
}
@@ -148,8 +148,9 @@ static void virtio_config_enable(struct virtio_device *dev)
{
spin_lock_irq(&dev->config_lock);
dev->config_enabled = true;
- __virtio_config_changed(dev);
- dev->config_changed = false;
+ if (dev->config_change_pending)
+ __virtio_config_changed(dev);
+ dev->config_change_pending = false;
spin_unlock_irq(&dev->config_lock);
}
@@ -253,7 +254,7 @@ int register_virtio_device(struct virtio_device *dev)
spin_lock_init(&dev->config_lock);
dev->config_enabled = false;
- dev->config_changed = false;
+ dev->config_change_pending = false;
/* We always start by resetting the device, in case a previous
* driver messed it up. This also tests that code path a little. */
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 5636b119dc25..65261a7244fc 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -80,7 +80,7 @@ bool virtqueue_is_broken(struct virtqueue *vq);
* @index: unique position on the virtio bus
* @failed: saved value for CONFIG_S_FAILED bit (for restore)
* @config_enabled: configuration change reporting enabled
- * @config_changed: configuration change reported while disabled
+ * @config_change_pending: configuration change reported while disabled
* @config_lock: protects configuration change reporting
* @dev: underlying device.
* @id: the device type identification (used to match it with a driver).
@@ -94,7 +94,7 @@ struct virtio_device {
int index;
bool failed;
bool config_enabled;
- bool config_changed;
+ bool config_change_pending;
spinlock_t config_lock;
struct device dev;
struct virtio_device_id id;
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[PATCH v4 04/25] virtio: defer config changed notifications
Defer config changed notifications that arrive during
probe/scan/freeze/restore.
This will allow drivers to set DRIVER_OK earlier, without worrying about
racing with config change interrupts.
This change will also benefit old hypervisors (before 2009)
that send interrupts without checking DRIVER_OK: previously,
the callback could race with driver-specific initialization.
This will also help simplify drivers.
Signed-off-by: Michael S. Tsirkin
Reviewed-by: Cornelia Huck
---
include/linux/virtio.h | 6 ++
drivers/virtio/virtio.c | 57 +
2 files changed, 54 insertions(+), 9 deletions(-)
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 8df7ba8..5636b11 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -79,6 +79,9 @@ bool virtqueue_is_broken(struct virtqueue *vq);
* virtio_device - representation of a device using virtio
* @index: unique position on the virtio bus
* @failed: saved value for CONFIG_S_FAILED bit (for restore)
+ * @config_enabled: configuration change reporting enabled
+ * @config_changed: configuration change reported while disabled
+ * @config_lock: protects configuration change reporting
* @dev: underlying device.
* @id: the device type identification (used to match it with a driver).
* @config: the configuration ops for this device.
@@ -90,6 +93,9 @@ bool virtqueue_is_broken(struct virtqueue *vq);
struct virtio_device {
int index;
bool failed;
+ bool config_enabled;
+ bool config_changed;
+ spinlock_t config_lock;
struct device dev;
struct virtio_device_id id;
const struct virtio_config_ops *config;
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 8216b73..2536701 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -117,6 +117,42 @@ void virtio_check_driver_offered_feature(const struct
virtio_device *vdev,
}
EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);
+static void __virtio_config_changed(struct virtio_device *dev)
+{
+ struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+
+ if (!dev->config_enabled)
+ dev->config_changed = true;
+ else if (drv && drv->config_changed)
+ drv->config_changed(dev);
+}
+
+void virtio_config_changed(struct virtio_device *dev)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dev->config_lock, flags);
+ __virtio_config_changed(dev);
+ spin_unlock_irqrestore(&dev->config_lock, flags);
+}
+EXPORT_SYMBOL_GPL(virtio_config_changed);
+
+static void virtio_config_disable(struct virtio_device *dev)
+{
+ spin_lock_irq(&dev->config_lock);
+ dev->config_enabled = false;
+ spin_unlock_irq(&dev->config_lock);
+}
+
+static void virtio_config_enable(struct virtio_device *dev)
+{
+ spin_lock_irq(&dev->config_lock);
+ dev->config_enabled = true;
+ __virtio_config_changed(dev);
+ dev->config_changed = false;
+ spin_unlock_irq(&dev->config_lock);
+}
+
static int virtio_dev_probe(struct device *_d)
{
int err, i;
@@ -153,6 +189,8 @@ static int virtio_dev_probe(struct device *_d)
add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
if (drv->scan)
drv->scan(dev);
+
+ virtio_config_enable(dev);
}
return err;
@@ -163,6 +201,8 @@ static int virtio_dev_remove(struct device *_d)
struct virtio_device *dev = dev_to_virtio(_d);
struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+ virtio_config_disable(dev);
+
drv->remove(dev);
/* Driver should have reset device. */
@@ -211,6 +251,10 @@ int register_virtio_device(struct virtio_device *dev)
dev->index = err;
dev_set_name(&dev->dev, "virtio%u", dev->index);
+ spin_lock_init(&dev->config_lock);
+ dev->config_enabled = false;
+ dev->config_changed = false;
+
/* We always start by resetting the device, in case a previous
* driver messed it up. This also tests that code path a little. */
dev->config->reset(dev);
@@ -239,20 +283,13 @@ void unregister_virtio_device(struct virtio_device *dev)
}
EXPORT_SYMBOL_GPL(unregister_virtio_device);
-void virtio_config_changed(struct virtio_device *dev)
-{
- struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
-
- if (drv && drv->config_changed)
- drv->config_changed(dev);
-}
-EXPORT_SYMBOL_GPL(virtio_config_changed);
-
#ifdef CONFIG_PM_SLEEP
int virtio_device_freeze(struct virtio_device *dev)
{
struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+ virtio_config_disable(dev);
+
dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
if (drv && drv->freeze)
@@ -297,6 +334,8 @@ int virtio_device_restore(struct virtio_device *dev)
/* Finally, tell the device we're all set */
