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    SubjectRe: [PATCH v2] xen/pciback: support driver_override
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    On 08/09/16 16:10, Boris Ostrovsky wrote:
    > On 09/02/2016 08:30 AM, Juergen Gross wrote:
    >> Support the driver_override scheme introduced with commit 782a985d7af2
    >> ("PCI: Introduce new device binding path using pci_dev.driver_override")
    >>
    >> As pcistub_probe() is called for all devices (it has to check for a
    >> match based on the slot address rather than device type) it has to
    >> check for driver_override set to "pciback" itself.
    >>
    >> Signed-off-by: Juergen Gross <jgross@suse.com>
    >> ---
    >> V2: removed now unused label
    >> ---
    >> drivers/xen/xen-pciback/pci_stub.c | 16 ++++++++++------
    >> 1 file changed, 10 insertions(+), 6 deletions(-)
    >>
    >> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
    >> index 258b7c3..85c28f7 100644
    >> --- a/drivers/xen/xen-pciback/pci_stub.c
    >> +++ b/drivers/xen/xen-pciback/pci_stub.c
    >> @@ -25,6 +25,8 @@
    >> #include "conf_space.h"
    >> #include "conf_space_quirks.h"
    >>
    >> +#define PCISTUB_DRIVER_NAME "pciback"
    >> +
    >> static char *pci_devs_to_hide;
    >> wait_queue_head_t xen_pcibk_aer_wait_queue;
    >> /*Add sem for sync AER handling and xen_pcibk remove/reconfigue ops,
    >> @@ -529,16 +531,18 @@ static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
    >> "don't have a normal (0) or bridge (1) "
    >> "header type!\n");
    >> err = -ENODEV;
    >> - goto out;
    >> }
    >>
    >> + } else if (!dev->driver_override ||
    >> + strcmp(dev->driver_override, PCISTUB_DRIVER_NAME))
    >> + /* Didn't find the device */
    >> + err = -ENODEV;
    >> +
    >> + if (!err) {
    >> dev_info(&dev->dev, "seizing device\n");
    >> err = pcistub_seize(dev);
    >> - } else
    >> - /* Didn't find the device */
    >> - err = -ENODEV;
    >> + }
    >
    > Should devices with pciback override be displayed in
    > /sys/bus/pci/drivers/pciback/slots? If they should then they need to be
    > either added to pcistub_device_ids or kept on some other list.

    No, I don't think so. The patch is just needed to _avoid_ having to use
    the slots stuff: without the patch you need something like:

    echo 0000:07:10.0 > /sys/bus/pci/devices/0000\:07\:10.0/driver/unbind
    echo 0000:07:10.0 > /sys/bus/pci/drivers/pciback/new_slot
    echo 0000:07:10.0 > /sys/bus/pci/drivers_probe

    while with the patch you can use the same mechanism as for similar
    drivers like pci-stub and vfio-pci:

    echo pciback > /sys/bus/pci/devices/0000\:07\:10.0/driver_override
    echo 0000:07:10.0 > /sys/bus/pci/devices/0000\:07\:10.0/driver/unbind
    echo 0000:07:10.0 > /sys/bus/pci/drivers_probe

    So e.g. libvirt doesn't need special handling for pciback. The slot list
    is necessary for assigning devices to pciback on boot, but I think the
    override mechanism is better for runtime assignment.

    > Also, do you think checking override might better be done first, before
    > testing for ID match?

    Why? I don't think this really matters.


    Juergen

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