Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | Re: [Xen-devel] Regression due to "device property: Make it possible to use secondary firmware nodes" Re: Xen-unstable + linux 4.1-mergewindow: problems with PV guest pci passthrough: pcifront pci-0: pciback not responding!!! | Date | Tue, 26 May 2015 01:42:16 +0200 |
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On Tuesday, May 26, 2015 01:22:12 AM Rafael J. Wysocki wrote: > On Friday, May 22, 2015 09:53:37 PM Boris Ostrovsky wrote: > > On 05/22/2015 04:11 AM, Sander Eikelenboom wrote: > > > Hello Sander, > > >
[cut]
> > (+Rafael again) > > > > So the immediate cause of those errors is that pdev->evtchn is 0. > > Backend is not notified and things not go well then. > > > > And it is indeed caused by 97badf873ab60e841243b66133ff9eff2a46ef29: > > > > We allocate pcifront_sd in pcifront_scan_root() and then pass it to > > pci_scan_bus_parented() as sysdata. Eventually this sysdata is used in > > pcibios_root_bridge_prepare() as pci_sysdata. It is dereferenced as > > pci_sysdata->companion (which I believe is aliased to pcifront_sd->pdev)
Well, there is an int node field between them, so I'm not sure.
> > and then set_primary_fwnode() writes it, thus corrupting > > pcifront_sd->pdev (and I think this is what sets evtchn to zero).
So the corruption happens when set_primary_fwnode() writes NULL to the 'secondary' field of object pointed to by 'fwnode'.
This isn't strictly necessary and we might avoid the crash by only writing to fwnode->secondary if fn is not NULL.
So, Sander please test the patch below too if possible.
Of course, that doesn't solve a problem of passing an incorrect pointer to ACPI_COMPANION_SET() in pcibios_root_bridge_prepare().
--- drivers/base/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
Index: linux-pm/drivers/base/core.c =================================================================== --- linux-pm.orig/drivers/base/core.c +++ linux-pm/drivers/base/core.c @@ -2167,7 +2167,9 @@ void set_primary_fwnode(struct device *d if (fwnode_is_primary(fn)) fn = fn->secondary; - fwnode->secondary = fn; + if (fn) + fwnode->secondary = fn; + dev->fwnode = fwnode; } else { dev->fwnode = fwnode_is_primary(dev->fwnode) ?
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