Re: [Xen-devel] [PATCH 3/3] libxl: don't try to manipulate json config for stubdomain

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Oct 19, 2016 at 10:38:04AM +0100, Wei Liu wrote:
> On Tue, Oct 18, 2016 at 03:53:33AM +0200, Marek Marczykowski-Górecki wrote:
> > Stubdomain do not have it's own config file - its configuration is
> > derived from target domains. Do not try to manipulate it when attaching
> > PCI device.
> > 
> > This bug prevented starting HVM with stubdomain and PCI passthrough
> > device attached.
> > 
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >  tools/libxl/libxl_pci.c | 24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> > 
> > diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
> > index 3805d30..5ad70c5 100644
> > --- a/tools/libxl/libxl_pci.c
> > +++ b/tools/libxl/libxl_pci.c
> > @@ -151,14 +151,18 @@ static int libxl__device_pci_add_xenstore(libxl__gc 
> > *gc, uint32_t domid, libxl_d
> >      GCNEW(device);
> >      libxl__device_from_pcidev(gc, domid, pcidev, device);
> >  
> > -    lock = libxl__lock_domain_userdata(gc, domid);
> > -    if (!lock) {
> > -        rc = ERROR_LOCK_FAIL;
> > -        goto out;
> > -    }
> > +    /* Stubdomain config is derived from its target domain, it doesn't have
> > +       its own file */
> > +    if (!libxl_is_stubdom(CTX, domid, NULL)) {
> > +        lock = libxl__lock_domain_userdata(gc, domid);
> > +        if (!lock) {
> > +            rc = ERROR_LOCK_FAIL;
> > +            goto out;
> > +        }
> >  
> 
> What makes PCI devices special with regard to other devices? In other
> words, do we need to make similar changes to other devices as well?

I think PCI is special because libxl doesn't bother to update stubdomain
configuration for other device types at all... If I try dynamic
attach of network device to a HVM (with stubdomain), it gets attached
_only_ to the target domain. So HVM without any PV drivers is out of
luck. Is it supposed to work with qemu in dom0?

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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