Re: [Qemu-devel] [PULL 00/20] acpi,pc,pci fixes and enhancements

[Paolo Bonzini]

Il 18/02/2014 13:45, Stefano Stabellini ha scritto:
> Disk unplug: hw/ide/piix.c:pci_piix3_xen_ide_unplug (see the beginning
> of the email :-P).
> It is called by hw/xen/xen_platform.c:platform_fixed_ioport_writew, in
> response to the guest writing to a magic ioport specifically to unplug
> the emulated disk.
> With this patch after the guest boots I can still access both xvda and
> sda for the same disk, leading to fs corruptions.

Ok, the last paragraph is what I was missing.

So this is dc->unplug for the PIIX3 IDE device.  Because PCI declares a 
hotplug handler, dc->unplug is not called anymore.

But unlike other dc->unplug callbacks, pci_piix3_xen_ide_unplug doesn't 
free the device, it just drops the disks underneath.  I think the 
simplest solution is to _not_ make it a dc->unplug callback at all, and 
call pci_piix3_xen_ide_unplug from unplug_disks instead of qdev_unplug. 
 qdev_unplug means "ask guest to start unplug", which is not what Xen 
wants to do here.

Paolo