Re: [RFC PATCH V2 09/10] Qemu/VFIO: Add SRIOV VF migration support

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 25, 2015 at 11:32:23PM +0800, Lan, Tianyu wrote:
> 
> On 11/25/2015 5:03 AM, Michael S. Tsirkin wrote:
> >>>+void vfio_migration_cap_handle(PCIDevice *pdev, uint32_t addr,
> >>>+                                  uint32_t val, int len)
> >>>+{
> >>>+    VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
> >>>+
> >>>+    if (addr == vdev->migration_cap + PCI_VF_MIGRATION_VF_STATUS
> >>>+        && val == PCI_VF_READY_FOR_MIGRATION) {
> >>>+        qemu_event_set(&migration_event);
> >This would wake migration so it can proceed -
> >except it needs QEMU lock to run, and that's
> >taken by the migration thread.
> 
> Sorry, I seem to miss something.
> Which lock may cause dead lock when calling vfio_migration_cap_handle()
> and run migration?

qemu_global_mutex.

> The function is called when VF accesses faked PCI capability.
> 
> >
> >It seems unlikely that this ever worked - how
> >did you test this?
> >