[libvirt] [PATCH] qemu: Prevent isolation group-related guest disappearance

[Andrea Bolognani]

We can't retrieve the isolation group of a device that's
not present in the system. However, it's very common for
VFs to be created late in the boot, so they might not be
present yet when libvirtd starts, which would cause the
guests using them to disappear.

If a PCI address has already been set for the host device
in question, we can assume that it either existed at some
point in the past or the user is assigning addresses
manually: in both cases, we should not error out and just
ignore the (temporary) failure.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1484254

Signed-off-by: Andrea Bolognani <abologna at redhat.com>
---
 src/qemu/qemu_domain_address.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/qemu/qemu_domain_address.c b/src/qemu/qemu_domain_address.c
index 16bf0cdf9..7f12f186b 100644
--- a/src/qemu/qemu_domain_address.c
+++ b/src/qemu/qemu_domain_address.c
@@ -1012,6 +1012,18 @@ qemuDomainFillDeviceIsolationGroup(virDomainDefPtr def,
         tmp = virPCIDeviceAddressGetIOMMUGroupNum(hostAddr);
 
         if (tmp < 0) {
+            /* If there's already a PCI address assigned to the device
+             * we move on instead of erroring out.
+             *
+             * This means we still don't allow non-existing host
+             * devices to be assigned to guests; however, if the host
+             * device existed at some point in the past but no longer
+             * does, which can happen very easily when dealing with VFs,
+             * we prevent the guest from disappearing and give the user
+             * an opportunity to edit its configuration */
+            if (virDeviceInfoPCIAddressPresent(info))
+                goto skip;
+
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            _("Can't look up isolation group for host device "
                              "%04x:%02x:%02x.%x"),
-- 
2.13.5