Re: [QEMU][PATCH v1 1/7] xen: when unplugging emulated devices skip virtio devices

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Tue, 2023-10-10 at 13:24 -0700, Vikram Garhwal wrote:
> Hi Stefano,
> On Mon, Oct 09, 2023 at 04:51:53PM -0700, Stefano Stabellini wrote:
> > On Thu, 5 Oct 2023, Vikram Garhwal wrote:
> > > From: Juergen Gross <jgross@xxxxxxxx>
> > > 
> > > Virtio devices should never be unplugged at boot time, as they are
> > > similar to pci passthrough devices.
> > > 
> > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> > > ---
> > >  hw/i386/xen/xen_platform.c | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
> > > index 17457ff3de..3560eaf8c8 100644
> > > --- a/hw/i386/xen/xen_platform.c
> > > +++ b/hw/i386/xen/xen_platform.c
> > > @@ -28,6 +28,7 @@
> > >  #include "hw/ide/pci.h"
> > >  #include "hw/pci/pci.h"
> > >  #include "migration/vmstate.h"
> > > +#include "hw/virtio/virtio-bus.h"
> > >  #include "net/net.h"
> > >  #include "trace.h"
> > >  #include "sysemu/xen.h"
> > > @@ -132,7 +133,8 @@ static void unplug_nic(PCIBus *b, PCIDevice *d, void 
> > > *o)
> > >      /* We have to ignore passthrough devices */
> > >      if (pci_get_word(d->config + PCI_CLASS_DEVICE) ==
> > >              PCI_CLASS_NETWORK_ETHERNET
> > > -            && !pci_device_is_passthrough(d)) {
> > > +            && !pci_device_is_passthrough(d)
> > > +            && !qdev_get_child_bus(&d->qdev, TYPE_VIRTIO_BUS)) {
> > 
> > Please update the in-code comment above to say "ignore passthrough
> > devices and virtio devices"
>
> Sounds good. Will update in the code comment in v2.

Please could you also remove the note in docs/system/i386/xen.rst which
mentions having to dissuade the guest kernel from unplugging VirtIO
devices by adding 'xen_unplug_emul=never' to its command line?

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