On Thu, Mar 24, 2022 at 04:40:02PM +0800, Jason Wang wrote:
> From: Stefano Garzarella <sgarzare@xxxxxxxxxx>
>
> This avoids setting DRIVER_OK twice for those drivers that call
> virtio_device_ready() in the .restore
Is this trying to say it's faster?
If yes this one looks like a red herring. Yes we skip a write but we
replace it with a read which is not better performance-wise.
If we want to optimize this, it is better to just do that inside
virtio_add_status:
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 75c8d560bbd3..cd943c31bdbb 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -161,8 +161,14 @@ static void virtio_config_enable(struct virtio_device *dev)
void virtio_add_status(struct virtio_device *dev, unsigned int status)
{
+ unsigned int device_status;
+
might_sleep();
- dev->config->set_status(dev, dev->config->get_status(dev) | status);
+
+ device_status = dev->config->get_status(dev);
+
+ if (status & ~device_status)
+ dev->config->set_status(dev, device_status | status);
}
EXPORT_SYMBOL_GPL(virtio_add_status);
> and it will allows us to do
> extension on virtio_device_ready() without duplicating codes.
>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/virtio/virtio.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 22f15f444f75..75c8d560bbd3 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -526,8 +526,9 @@ int virtio_device_restore(struct virtio_device *dev)
> goto err;
> }
>
> - /* Finally, tell the device we're all set */
> - virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
> + /* If restore didn't do it, mark device DRIVER_OK ourselves. */
I preferred the original comment, it said why we are doing this,
new one repeats what code is doing.
> + if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
> + virtio_device_ready(dev);
>
> virtio_config_enable(dev);
>
> --
> 2.25.1
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