linux-kernel - Re: [PATCH v2 09/11] virtio: net: Add freeze, restore handlers to support S4

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Message-ID: <20111115143149.GE26378@amit-x200.redhat.com>
Date:	Tue, 15 Nov 2011 20:01:49 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	Virtualization List <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v2 09/11] virtio: net: Add freeze, restore handlers to
 support S4

On (Tue) 15 Nov 2011 [16:23:00], Michael S. Tsirkin wrote:
> On Tue, Nov 15, 2011 at 07:33:46PM +0530, Amit Shah wrote:
> > On (Tue) 15 Nov 2011 [14:51:27], Michael S. Tsirkin wrote:
> > > On Tue, Nov 15, 2011 at 05:59:36PM +0530, Amit Shah wrote:
> > > > On (Sun) 02 Oct 2011 [11:33:26], Michael S. Tsirkin wrote:
> > > > > On Thu, Sep 29, 2011 at 09:19:40PM +0530, Amit Shah wrote:
> > > > > > Remove all the vqs on hibernation and re-create them after restoring
> > > > > > from a hibernated image.  This keeps networking working across
> > > > > > hibernation.
> > > > > > 
> > > > > > Signed-off-by: Amit Shah <amit.shah@...hat.com>
> > > > > > ---
> > > > > >  drivers/net/virtio_net.c |   28 ++++++++++++++++++++++++++++
> > > > > >  1 files changed, 28 insertions(+), 0 deletions(-)
> > > > > > 
> > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > > > index dcd4b01..8b9ed43 100644
> > > > > > --- a/drivers/net/virtio_net.c
> > > > > > +++ b/drivers/net/virtio_net.c
> > > > > > @@ -1131,6 +1131,30 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
> > > > > >  	free_netdev(vi->dev);
> > > > > >  }
> > > > > >  
> > > > > > +#ifdef CONFIG_PM
> > > > > > +static int virtnet_freeze(struct virtio_device *vdev)
> > > > > > +{
> > > > > > +	struct virtnet_info *vi = vdev->priv;
> > > > > 
> > > > > I'm guessing we need to do something like netif_device_detach here,
> > > > > otherwise guest might be in the process of using the vq for transmit at
> > > > > this point.
> > > > 
> > > > Done.
> > > > 
> > > > > I think we also must make sure NAPI RX handler is not in progress.
> > > > 
> > > > How to do that?  napi_disable() / napi_enable() doesn't seem right
> > > > (and it doesn't work, too).  pci_disable_device() in the suspend
> > > > routine may work?
> > > > 
> > > > > We also might need to mask interrupts from the device
> > > > > to prevent TX or RX from getting rescheduled?
> > > > 
> > > > pci_disable_device() will help this too, right?
> > > > 
> > > 
> > > No, why would it help?
> > 
> > IRQs will be disabled after the call to pci_disable_device(),
> > isn't that sufficient?
> > 
> 
> They will?
>  * pci_disable_device - Disable PCI device after use
>  * @dev: PCI device to be disabled
>  *
>  * Signal to the system that the PCI device is not in use by the system
>  * anymore.  This only involves disabling PCI bus-mastering, if active.
>  *
>  * Note we don't actually disable the device until all callers of
>  * pci_enable_device() have called pci_disable_device().

You mean multiple devices could have called pci_enable_device()?  Not
likely to happen, at least in case of our virtio devices... only we
claim ownership over them.  I don't think that'll change.

		Amit
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