Re: [PATCH v2 2/4] libxl: attach PCI device to qemu only after setting pciback/pcifront

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Jan 17, 2019 at 11:29:59AM +0100, Roger Pau Monné wrote:
> On Tue, Jan 15, 2019 at 04:36:29PM +0100, Marek Marczykowski-Górecki wrote:
> > When qemu is running in stubdomain, handling "pci-ins" command will fail
> > if pcifront is not initialized already. Fix this by sending such command
> > only after confirming that pciback/front is running.
> > 
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> > ---
> > Changes in v2:
> > - Fixed code style since previous version.
> > ---
> >  tools/libxl/libxl_pci.c |  9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
> > index 3b6b23c..1bde537 100644
> > --- a/tools/libxl/libxl_pci.c
> > +++ b/tools/libxl/libxl_pci.c
> > @@ -1191,6 +1191,7 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, libxl_device_pci *pcide
> >  {
> >      libxl_ctx *ctx = libxl__gc_owner(gc);
> >      unsigned int orig_vdev, pfunc_mask;
> > +    char *be_path;
> >      libxl_device_pci *assigned;
> >      int num_assigned, i, rc;
> >      int stubdomid = 0;
> > @@ -1245,6 +1246,14 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, libxl_device_pci *pcide
> >          rc = do_pci_add(gc, stubdomid, &pcidev_s, 0);
> >          if ( rc )
> >              goto out;
> > +        /* Wait for the device actually being connected, otherwise device model
> > +         * running there will fail to find the device. */
> > +        be_path = libxl__sprintf(gc, "%s/backend/pci/%d/0",
> > +                                 libxl__xs_get_dompath(gc, 0), stubdomid);
> > +        rc = libxl__wait_for_backend(gc, be_path,
> > +                                     GCSPRINTF("%d", XenbusStateConnected));
> > +        if (rc)
> > +            goto out;
> 
> I think it would be better to use the async libxl functionality here,
> see libxl__xswait_start. I will leave for the toolstack maintainers to
> decide. Apart from that the change seems correct.

libxl__device_pci_add() is not async-aware right now and it looks like
converting it is quite a bit of work. I'd leave it out of scope for this
patch series...

-- 
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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