Re: [libvirt] [PATCH] qemu: Fix mdev checking for VFIO support

On Wed, Apr 12, 2017 at 12:26:35PM +0200, Erik Skultety wrote: > Commit a4a39d90 added a check that checks for VFIO support with mediated > devices. The problem is that the hostdev preparing functions behave like > a fallthrough if device of that specific type doesn't exist. However, > the check for VFIO support was independent of the existence of a mdev > device which caused the guest to fail to start with any device to be > directly assigned if VFIO was disabled/unavailable in the kernel. > The proposed change first ensures that it makes sense to check for VFIO > support in the first place, and only then performs the VFIO support check > itself. > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1441291 > > Signed-off-by: Erik Skultety <eskultet(a)redhat.com&gt; > --- > src/qemu/qemu_hostdev.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/src/qemu/qemu_hostdev.c b/src/qemu/qemu_hostdev.c > index 685bf5b59..9b5504832 100644 > --- a/src/qemu/qemu_hostdev.c > +++ b/src/qemu/qemu_hostdev.c > @@ -330,11 +330,19 @@ qemuHostdevPrepareMediatedDevices(virQEMUDriverPtr driver, > int nhostdevs) > { > virHostdevManagerPtr hostdev_mgr = driver->hostdevMgr; > + bool supportsVFIO = qemuHostdevHostSupportsPassthroughVFIO(); > + size_t i; > > - if (!qemuHostdevHostSupportsPassthroughVFIO()) { > - virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", > - _("host doesn't support VFIO PCI interface")); > - return -1; > + for (i = 0; i < nhostdevs; i++) { > + if (hostdevs[i]->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS && > + hostdevs[i]->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_MDEV) { > + if (!supportsVFIO) { > + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", > + _("host doesn't support VFIO PCI interface")); BTW, I'd suggest changing that message to "Mediated host device assignment requires VFIO support" to make it clear what feature usage is triggering the error > + return -1; > + } > + break; > + } > } > > return virHostdevPrepareMediatedDevices(hostdev_mgr, QEMU_DRIVER_NAME, ACK,