Re: [Qemu-devel] [PATCH v3] xen: implement unplug protocol in xen_platform

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

On Fri, 1 Jul 2011, Stefano Stabellini wrote:
> On Fri, 1 Jul 2011, Kevin Wolf wrote:
> > Am 30.06.2011 16:16, schrieb Stefano Stabellini:
> > > On Thu, 30 Jun 2011, Kevin Wolf wrote:
> > >>> +static int pci_piix3_xen_ide_unplug(DeviceState *dev)
> > >>> +{
> > >>> +    PCIDevice *pci_dev;
> > >>> +    PCIIDEState *pci_ide;
> > >>> +    DriveInfo *di;
> > >>> +    int i = 0;
> > >>> +
> > >>> +    pci_dev = DO_UPCAST(PCIDevice, qdev, dev);
> > >>> +    pci_ide = DO_UPCAST(PCIIDEState, dev, pci_dev);
> > >>> +
> > >>> +    for (; i < 3; i++) {
> > >>> +        di = drive_get_by_index(IF_IDE, i);
> > >>> +        if (di != NULL && di->bdrv != NULL && !di->bdrv->removable) {
> > >>> +            DeviceState *ds = bdrv_get_attached(di->bdrv);
> > >>> +            if (ds) {
> > >>> +                bdrv_detach(di->bdrv, ds);
> > >>> +            }
> > >>> +            bdrv_close(di->bdrv);
> > >>> +            pci_ide->bus[di->bus].ifs[di->unit].bs = NULL;
> > >>
> > >> Have you tested if this is enough if the guest tries to continue using
> > >> the device? I don't know of any case where it's not sufficient, just
> > >> trying to make sure that it's really true in practice.
> > > 
> > > The purpose of this is to "hide" the disk from the guest. The unplug is
> > > supposed to happen *before* the guest enumerates the IDE disks; it is
> > > responsibility of the guest to make sure of it.
> > > I tested it with Linux PV on HVM drivers, and Linux doesn't see the
> > > emulated disk after the unplug, as it should be.
> > 
> > Yeah. What I meant is that we should make sure that a misbehaving guest,
> > which just keeps on playing with the IDE ports anyway, can't crash qemu.
> > A quick review suggests that it is the case, but testing it anyway would
> > be better.
> 
> I see what you mean: I tested it, a guest cannot crash Qemu.
> 

ping?