Messages in this thread | | | Date | Mon, 1 Dec 2014 14:14:56 +0000 | From | David Vrabel <> | Subject | Re: [Xen-devel] [PATCH v4 7/7] xen/pciback: Restore configuration space when detaching from a guest. |
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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@eikelenboom.it> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > --- > 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?
> + else { > + __pci_reset_function_locked(dev);
I think the reset should always be attempted regardless of whether the correct state was loaded or not.
David
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