On Thu, Sep 30, 2021 at 8:20 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Thu, Sep 30, 2021 at 7:38 PM Rafael J. Wysocki
> <rafael.j.wysocki@xxxxxxxxx> wrote:
> >
> > On 9/30/2021 7:31 PM, Jesse Brandeburg wrote:
> > > On 9/28/2021 4:56 AM, Niklas Schnelle wrote:
> > >> Hi Jesse, Hi Tony,
> > >>
> > >> Since v5.15-rc1 I've been having problems with enabling SR-IOV VFs on
> > >> my private workstation with an Intel 82599 NIC with the ixgbe driver. I
> > >> haven't had time to bisect or look closer but since it still happens on
> > >> v5.15-rc3 I wanted to at least check if you're aware of the problem as
> > >> I couldn't find anything on the web.
> > > We haven't heard anything of this problem.
> > >
> > >
> > >> I get below Oops when trying "echo 2 > /sys/bus/pci/.../sriov_numvfs"
> > >> and suspect that the earlier ACPI messages could have something to do
> > >> with that, absolutely not an ACPI expert though. If there is a need I
> > >> could do a bisect.
> > > Hi Niklas, thanks for the report, I added the Intel Driver's list for
> > > more exposure.
> > >
> > > I asked the developers working on that driver to take a look and they
> > > tried to reproduce, and were unable to do so. This might be related to
> > > your platform, which strongly suggests that the ACPI stuff may be related.
> > >
> > > We have tried to reproduce but everything works fine no call trace in
> > > scenario with creating VF.
> > >
> > > This is good in that it doesn't seem to be a general failure, you may
> > > want to file a kernel bugzilla (bugzilla.kernel.org) to track the issue,
> > > and I hope that @Rafael might have some insight.
> > >
> > > This issue may be related to changes in acpi_pci_find_companion,
> > > but as I say, we are not able to reproduce this.
> > >
> > > commit 59dc33252ee777e02332774fbdf3381b1d5d5f5d
> > > Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > Date: Tue Aug 24 16:43:55 2021 +0200
> > > PCI: VMD: ACPI: Make ACPI companion lookup work for VMD bus
> >
> > This change doesn't affect any devices beyond the ones on the VMD bus.
>
> The only failing case I can see is when the device is on the VMD bus
> and its bus pointer is NULL, so the dereference in
> vmd_acpi_find_companion() crashes.
>
> Can anything like that happen?
Not really, because pci_iov_add_virtfn() sets virtfn->bus.
However, it doesn\t set virtfn->dev.parent AFAICS, so when that gets
dereferenced by ACPI_COMPANIO(dev->parent) in
acpi_pci_find_companion(), the crash occurs.
We need a !dev->parent check in acpi_pci_find_companion() I suppose:
Does the following change help?
Index: linux-pm/drivers/pci/pci-acpi.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-acpi.c
+++ linux-pm/drivers/pci/pci-acpi.c
@@ -1243,6 +1243,9 @@ static struct acpi_device *acpi_pci_find
bool check_children;
u64 addr;
+ if (!dev->parent)
+ return NULL;
+
down_read(&pci_acpi_companion_lookup_sem);
adev = pci_acpi_find_companion_hook ?
