From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, maz@kernel.org, tglx@linutronix.de,
peterz@infradead.org, sgarzare@redhat.com, keirf@google.com
Subject: Re: [PATCH 1/3] virtio: use virtio_device_ready() in virtio_device_restore()
Date: Thu, 24 Mar 2022 06:48:05 -0400 [thread overview]
Message-ID: <20220324064205-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20220324084004.14349-2-jasowang@redhat.com>
On Thu, Mar 24, 2022 at 04:40:02PM +0800, Jason Wang wrote:
> From: Stefano Garzarella <sgarzare@redhat.com>
>
> 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@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> 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
next prev parent reply other threads:[~2022-03-24 10:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-24 8:40 [PATCH 0/3] rework on the IRQ hardening of virtio Jason Wang
2022-03-24 8:40 ` [PATCH 1/3] virtio: use virtio_device_ready() in virtio_device_restore() Jason Wang
2022-03-24 10:48 ` Michael S. Tsirkin [this message]
2022-03-24 11:03 ` Stefano Garzarella
2022-03-24 11:07 ` Michael S. Tsirkin
2022-03-24 11:31 ` Stefano Garzarella
2022-03-25 3:05 ` Jason Wang
2022-03-30 5:22 ` Michael S. Tsirkin
2022-03-24 8:40 ` [PATCH 2/3] virtio: use virtio_reset_device() when possible Jason Wang
2022-03-24 11:04 ` Stefano Garzarella
2022-03-24 8:40 ` [PATCH 3/3] virtio: harden vring IRQ Jason Wang
2022-03-24 11:03 ` Michael S. Tsirkin
2022-03-25 3:04 ` Jason Wang
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