From: "Michael S. Tsirkin" <mst@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-scsi@vger.kernel.org, linux-s390@vger.kernel.org,
v9fs-developer@lists.sourceforge.net, netdev@vger.kernel.org,
kvm@vger.kernel.org, Amit Shah <amit.shah@redhat.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
"David S. Miller" <davem@davemloft.net>,
Paolo Bonzini <pbonzini@redhat.com>,
Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Subject: Re: [PATCH v4 04/25] virtio: defer config changed notifications
Date: Tue, 14 Oct 2014 11:59:08 +0300 [thread overview]
Message-ID: <20141014085908.GA6016@redhat.com> (raw)
In-Reply-To: <87lhojcx0v.fsf@rustcorp.com.au>
On Tue, Oct 14, 2014 at 11:01:12AM +1030, Rusty Russell wrote:
> "Michael S. Tsirkin" <mst@redhat.com> 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;
next prev parent reply other threads:[~2014-10-14 8:55 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-13 7:48 [PATCH v4 00/25] virtio: fix spec compliance issues Michael S. Tsirkin
2014-10-13 7:48 ` [PATCH v4 01/25] virtio_pci: fix virtio spec compliance on restore Michael S. Tsirkin
2014-10-13 7:48 ` [PATCH v4 02/25] virtio: unify config_changed handling Michael S. Tsirkin
2014-10-13 7:48 ` [PATCH v4 03/25] virtio-pci: move freeze/restore to virtio core Michael S. Tsirkin
2014-10-15 7:05 ` Paul Bolle
2014-10-13 7:50 ` [PATCH v4 04/25] virtio: defer config changed notifications Michael S. Tsirkin
2014-10-14 0:31 ` Rusty Russell
2014-10-14 8:59 ` Michael S. Tsirkin [this message]
2014-10-13 7:50 ` [PATCH v4 05/25] virtio_blk: drop config_enable Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 06/25] virtio-blk: drop config_mutex Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 07/25] virtio_net: drop config_enable Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 08/25] virtio-net: drop config_mutex Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 09/25] virtio_net: minor cleanup Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 10/25] virtio: add API to enable VQs early Michael S. Tsirkin
2014-11-11 0:45 ` Andy Grover
2014-11-11 6:15 ` Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 11/25] virtio_net: " Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 12/25] virtio_blk: " Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 13/25] virtio_console: " Michael S. Tsirkin
2014-10-20 12:07 ` Thomas Graf
2014-10-20 12:42 ` Cornelia Huck
2014-10-20 13:10 ` Thomas Graf
2014-10-20 13:35 ` Michael S. Tsirkin
2014-10-20 13:58 ` [PATCH] virtio_console: move early VQ enablement Cornelia Huck
2014-10-20 14:05 ` Michael S. Tsirkin
2014-10-20 17:09 ` Josh Boyer
2014-11-11 2:24 ` Dave Airlie
2014-10-20 14:04 ` [PATCH v4 13/25] virtio_console: enable VQs early Michael S. Tsirkin
2014-10-20 13:10 ` Michael S. Tsirkin
2014-10-20 13:12 ` Thomas Graf
2014-10-20 13:14 ` Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 14/25] 9p/trans_virtio: " Michael S. Tsirkin
2014-10-13 7:50 ` [PATCH v4 15/25] virtio_net: fix use after free on allocation failure Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 16/25] virtio_scsi: move kick event out from virtscsi_init Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 17/25] virtio_blk: enable VQs early on restore Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 18/25] virtio_scsi: " Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 19/25] virtio_console: " Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 20/25] virtio_net: " Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 21/25] virito_scsi: use freezable WQ for events Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 22/25] virtio_scsi: fix race on device removal Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 23/25] virtio_balloon: enable VQs early on restore Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 24/25] virtio_scsi: drop scan callback Michael S. Tsirkin
2014-10-13 7:51 ` [PATCH v4 25/25] virtio-rng: refactor probe error handling Michael S. Tsirkin
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