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    SubjectRe: [v2] PCI: Add an option to control probing of VFs before enabling SR-IOV
    Hi Bodong,

    On Wed, Mar 22, 2017 at 05:53:58PM +0200, bodong@mellanox.com wrote:
    > From: Bodong Wang <bodong@mellanox.com>
    >
    > Sometimes it is not desirable to probe the virtual functions after
    > SRIOV is enabled. This can save host side resource usage by VF
    > instances which would be eventually probed to VMs.
    >
    > Add a new PCI sysfs interface "sriov_probe_vfs" to control that
    > from the PF, all current callers still retain the same functionality.
    > To modify it, echo 0/n/N (disable probe) or 1/y/Y (enable probe) to
    >
    > /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_probe_vfs

    Is this basically the same functionality as /sys/bus/pci/drivers_autoprobe,
    but limited to a specific PF? I.e., could we accomplish the same thing
    with the following?

    # echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvfs
    # echo 0 > /sys/bus/pci/drivers_autoprobe
    # echo 2 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvfs
    # echo 1 > /sys/bus/pci/drivers_autoprobe

    If not, can you contrast the above with drivers_autoprobe? If we need
    both, should they be named more similarly?

    > Note that, the choice must be made before enabling VFs. The change
    > will not take effect if VFs are already enabled. Simply, one can set
    > sriov_numvfs to 0, choose whether to probe or not, and then resume
    > sriov_numvfs.
    >
    > Signed-off-by: Bodong Wang <bodong@mellanox.com>
    > Signed-off-by: Eli Cohen <eli@mellanox.com>
    > Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>

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