Re: [PATCH] vfio: Set PCI_DEV_FLAGS_ASSIGNED when assigning device to guest

[Bandan Das <bsd@redhat.com>]

Alex Williamson <alex.williamson@redhat.com> writes:

> [cc +linux-pci]
>
> On Thu, 2014-01-30 at 10:33 -0700, Alex Williamson wrote:
>> On Thu, 2014-01-30 at 22:54 +0530, Bandan Das wrote:
>> > Some drivers such as ixgbe rely on pci_vfs_assigned() to prevent
>> > disabling sr-iov when vfs are still assigned during hotplug
>> > event or module removal. Set and unset PCI_DEV_FLAGS_ASSIGNED
>> > appropriately
>> 
>> This flag has always felt like a band-aide for KVM device assignment
>> because a device could be used without an actual driver attached to the
>> device.  vfio-pci is an actual driver, so why should it matter whether
>> the device is assigned or in use by ixgbevf or in use by pci-vfio?  It
>> seems like sr-iov shouldn't be disabled so long as either a driver or
>> this (needs to be deprecated) flag are set.  Thanks,

With cases such as vfio-pci, not having this flag set will disable sriov
while a guest is using it resulting in a hung guest. I am unfamiliar if 
similar scenarios are applicable to other test cases. If the flag needs
to be set, what's a better place then ? Or how does the PF driver decide not 
to disable sr-iov, should it be based on - as long as the device is bound to 
a driver ?

Bandan

>> Alex
>> 
>> > ---
>> >  drivers/vfio/pci/vfio_pci.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> > 
>> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> > index 7ba0424..7cc7ed6 100644
>> > --- a/drivers/vfio/pci/vfio_pci.c
>> > +++ b/drivers/vfio/pci/vfio_pci.c
>> > @@ -90,6 +90,7 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
>> >  		vdev->has_vga = true;
>> >  #endif
>> >  
>> > +	pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
>> >  	return 0;
>> >  }
>> >  
>> > @@ -149,6 +150,7 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
>> >  				__func__, dev_name(&pdev->dev), ret);
>> >  	}
>> >  
>> > +	pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
>> >  	pci_restore_state(pdev);
>> >  }
>> >  
>> 
>> 
>
>
>
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