Re: [libvirt] [PATCH] Fix device assignment with root devices

On Thu, Jan 21, 2010 at 11:33:21AM -0500, Chris Lalancette wrote: > The patches to add ACS checking to PCI device passthrough > introduced a bug. With the current code, if you try to > passthrough a device on the root bus (i.e. bus 0), then > it denies the passthrough. This is because the code in > pciDeviceIsBehindSwitchLackingACS() to check for a parent > device doesn't take into account the possibility of the > root bus. If we are on the root bus, it means we > legitimately can't find a parent, and it also means that > we don't have to worry about whether ACS is enabled. > Therefore return 0 (indicating we don't lack ACS) from > pciDeviceIsBehindSwitchLackingACS(). > > Signed-off-by: Chris Lalancette <clalance(a)redhat.com&gt; > --- > src/util/pci.c | 19 ++++++++++++++----- > 1 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/src/util/pci.c b/src/util/pci.c > index 086b751..0defbfe 100644 > --- a/src/util/pci.c > +++ b/src/util/pci.c > @@ -1198,11 +1198,20 @@ pciDeviceIsBehindSwitchLackingACS(virConnectPtr conn, > { > pciDevice *parent; > > - if (!(parent = pciGetParentDevice(conn, dev))) { > - pciReportError(conn, VIR_ERR_NO_SUPPORT, > - _("Failed to find parent device for %s"), > - dev->name); > - return -1; > + parent = pciGetParentDevice(conn, dev); > + if (!parent) { > + /* if we have no parent, and this is the root bus, ACS doesn't come > + * into play since devices on the root bus can't P2P without going > + * through the root IOMMU. > + */ > + if (dev->bus == 0) > + return 0; > + else { > + pciReportError(conn, VIR_ERR_NO_SUPPORT, > + _("Failed to find parent device for %s"), > + dev->name); > + return -1; > + } > } > > /* XXX we should rather fail when we can't find device's parent and ACK,