Stop if tracking is disable after it was enabled before

We don't support enabling and then later disabling
[pci]report_in_placement. This patch adds a check that kills the
nova-compute service is such situation.

The implementation rely on an extra trait
COMPUTE_MANAGED_PCI_DEVICE that is added to every PCI RP
automatically. Note that we cannot use the existing OWNER_NOVA standard
trait as that will be exists on other RPs in RP three. Also we cannot
use the naming scheme of the PCI RPs as cyborg is free to use the same
scheme and also nova might want to use that for VGPUs / MDEVs in the future.

Depends-On: https://review.opendev.org/c/openstack/os-traits/+/850538
blueprint: pci-device-tracking-in-placement
Change-Id: I6e68d7754cee51525894c14a74a554d82a648d8d

1 files changed, 26 insertions, 3 deletions

diff --git a/nova/compute/pci_placement_translator.py b/nova/compute/pci_placement_translator.py
index c97647be47..078a0b354f 100644
--- a/nova/compute/pci_placement_translator.py
+++ b/nova/compute/pci_placement_translator.py
@@ -73,10 +73,12 @@ def _get_traits_for_dev(
     # traits is a comma separated list of placement trait names
     traits_str = dev_spec_tags.get("traits")
     if not traits_str:
-        return set()
+        return {os_traits.COMPUTE_MANAGED_PCI_DEVICE}
 
     traits = traits_str.split(',')
-    return set(_normalize_traits(traits))
+    return set(_normalize_traits(traits)) | {
+        os_traits.COMPUTE_MANAGED_PCI_DEVICE
+    }
 
 
 def _get_rc_for_dev(
@@ -211,7 +213,7 @@ class PciResourceProvider:
         if self.devs:
             return (
                 f"RP({self.name}, {self.resource_class}={len(self.devs)}, "
-                f"traits={','.join(self.traits or set())})"
+                f"traits={','.join(sorted(self.traits or set()))})"
             )
         else:
             return f"RP({self.name}, <EMPTY>)"
@@ -357,6 +359,26 @@ def ensure_no_dev_spec_with_devname(dev_specs: ty.List[devspec.PciDeviceSpec]):
             raise exception.PlacementPciException(error=msg)
 
 
+def ensure_tracking_was_not_enabled_before(
+    provider_tree: provider_tree.ProviderTree
+) -> None:
+    # If placement tracking was enabled before then we do not support
+    # disabling it later. To check for that we can look for RPs with
+    # the COMPUTE_MANAGED_PCI_DEVICE trait. If any then we raise to
+    # kill the service
+    for rp_uuid in provider_tree.get_provider_uuids():
+        if (
+            os_traits.COMPUTE_MANAGED_PCI_DEVICE
+            in provider_tree.data(rp_uuid).traits
+        ):
+            msg = _(
+                "The [pci]report_in_placement is False but it was enabled "
+                "before on this compute. Nova does not support disabling "
+                "it after it is enabled."
+            )
+            raise exception.PlacementPciException(error=msg)
+
+
 def update_provider_tree_for_pci(
     provider_tree: provider_tree.ProviderTree,
     nodename: str,
@@ -393,6 +415,7 @@ def update_provider_tree_for_pci(
               }
     """
     if not _is_placement_tracking_enabled():
+        ensure_tracking_was_not_enabled_before(provider_tree)
         # If tracking is not enabled we just return without touching anything
         return False