[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4 7/7] xen/pciback: Restore configuration space when detaching from a guest.
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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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