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    SubjectRe: [PATCH v2 3/3] vfio/pci: Don't probe devices that can't be reset
    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,

    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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