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SubjectRe: [PATCH v2 3/3] vfio/pci: Don't probe devices that can't be reset
On Thu, Aug 17, 2017 at 07:00:17AM -0600, Alex Williamson wrote:
> On Thu, 17 Aug 2017 10:14:23 +0200
> Jan Glauber <jglauber@cavium.com> wrote:
>
> > If a PCI device supports neither function-level reset, nor slot
> > or bus reset then refuse to probe it. A line is printed to inform
> > the user.
>
> But that's not what this does, this requires that the device is on a
> reset-able bus. This is a massive regression. With this we could no
> longer assign devices on the root complex or any device which doesn't
> return from bus reset and currently makes use of the NO_BUS_RESET flag
> and works happily otherwise. Full NAK. Thanks,

Looks like I missed the slot reset check. So how about this:

if (pci_probe_reset_slot(pdev->slot) && pci_probe_reset_bus(pdev->bus)) {
dev_warn(...);
return -ENODEV;
}

Or am I still missing something here?

thanks,
Jan

> Alex
>
> > Without this change starting qemu with a vfio-pci device can lead to
> > a kernel panic on some Cavium cn8xxx systems, depending on the used
> > device.
> >
> > Signed-off-by: Jan Glauber <jglauber@cavium.com>
> > ---
> > drivers/vfio/pci/vfio_pci.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index 063c1ce..029ba13 100644
> > --- a/drivers/vfio/pci/vfio_pci.c
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -1196,6 +1196,12 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
> > return -EINVAL;
> >
> > + ret = pci_probe_reset_bus(pdev->bus);
> > + if (ret) {
> > + dev_warn(&pdev->dev, "Refusing to probe because reset is not possible.\n");
> > + return ret;
> > + }
> > +
> > group = vfio_iommu_group_get(&pdev->dev);
> > if (!group)
> > return -EINVAL;

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