On Mon, Dec 01, 2014 at 02:14:56PM +0000, David Vrabel wrote:
> On 21/11/14 22:17, Konrad Rzeszutek Wilk wrote:
> > The commit "xen/pciback: Don't deadlock when unbinding." was using
> > the version of pci_reset_function which would lock the device lock.
> > That is no good as we can dead-lock. As such we swapped to using
> > the lock-less version and requiring that the callers
> > of 'pcistub_put_pci_dev' take the device lock. And as such
> > this bug got exposed.
> >
> > Using the lock-less version is OK, except that we tried to
> > use 'pci_restore_state' after the lock-less version of
> > __pci_reset_function_locked - which won't work as 'state_saved'
> > is set to false. Said 'state_saved' is a toggle boolean that
> > is to be used by the sequence of a) pci_save_state/pci_restore_state
> > or b) pci_load_and_free_saved_state/pci_restore_state. We don't
> > want to use a) as the guest might have messed up the PCI
> > configuration space and we want it to revert to the state
> > when the PCI device was binded to us. Therefore we pick
> > b) to restore the configuration space.
> >
> > We restore from our 'golden' version of PCI configuration space, when an:
> > - Device is unbinded from pciback
> > - Device is detached from a guest.
> >
> > Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > ---
> > drivers/xen/xen-pciback/pci_stub.c | 20 ++++++++++++++++----
> > 1 file changed, 16 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> > index 843a2ba..eb8b58e 100644
> > --- a/drivers/xen/xen-pciback/pci_stub.c
> > +++ b/drivers/xen/xen-pciback/pci_stub.c
> > @@ -105,7 +105,7 @@ static void pcistub_device_release(struct kref *kref)
> > */
> > __pci_reset_function_locked(dev);
> > if (pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state))
> > - dev_dbg(&dev->dev, "Could not reload PCI state\n");
> > + dev_info(&dev->dev, "Could not reload PCI state\n");
>
> Why dev_info when...
>
> > @@ -279,9 +281,19 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
> > * (so it's ready for the next domain)
> > */
> > device_lock_assert(&dev->dev);
> > - __pci_reset_function_locked(dev);
> > - pci_restore_state(dev);
> > -
> > + dev_data = pci_get_drvdata(dev);
> > + ret = pci_load_saved_state(dev, dev_data->pci_saved_state);
> > + if (ret < 0)
> > + dev_warn(&dev->dev, "Could not reload PCI state\n");
>
> ... this one is dev_warn?
Should be the same, dev_info I think?
>
> > + else {
> > + __pci_reset_function_locked(dev);
>
> I think the reset should always be attempted regardless of whether the
> correct state was loaded or not.
/me nods. Will redo it as such.
>
> David
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