Re: [Xen-devel] [PATCH 1/3] libxl: attach xen-pciback only to PV domains

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Tue, Oct 18, 2016 at 04:52:29PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Oct 18, 2016 at 03:53:31AM +0200, Marek Marczykowski-Górecki wrote:
> > HVM domains use IOMMU and device model assistance for communicating with
> > PCI devices, xen-pcifront/pciback is used only in PV domains.
> > When HVM domain has device model in stubdomain, attaching xen-pciback to
> > the target domain itself is not only useless, but also may prevent
> > attaching xen-pciback to the stubdomain, effectively breaking PCI
> > passthrough.
> 
> This has the consequence that the "reset" of the device that
> pciback does will no longer be done.
> 
> That is the FLR functionality will not be exercised anymore.

Are you sure about that? libxl__device_pci_add calls
libxl__device_pci_reset, regardless of my patch.

> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >  tools/libxl/libxl_pci.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
> > index 6f8f49c..2ae1bc4 100644
> > --- a/tools/libxl/libxl_pci.c
> > +++ b/tools/libxl/libxl_pci.c
> > @@ -1111,7 +1111,7 @@ out:
> >          }
> >      }
> >  
> > -    if (!starting)
> > +    if (!starting && !hvm)
> >          rc = libxl__device_pci_add_xenstore(gc, domid, pcidev, starting);
> >      else
> >          rc = 0;
> > @@ -1306,7 +1306,8 @@ static void libxl__add_pcidevs(libxl__egc *egc, 
> > libxl__ao *ao, uint32_t domid,
> >          }
> >      }
> >  
> > -    if (d_config->num_pcidevs > 0) {
> > +    if (d_config->num_pcidevs > 0
> > +            && d_config->c_info.type == LIBXL_DOMAIN_TYPE_PV) {
> >          rc = libxl__create_pci_backend(gc, domid, d_config->pcidevs,
> >              d_config->num_pcidevs);
> >          if (rc < 0) {
> > -- 
> > 2.5.5
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > https://lists.xen.org/xen-devel

-- 
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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