[libvirt] [PATCH v3 14/15] vircgroup: workaround devices in hybrid mode

[Pavel Hrdina]

So the issue here is that you can end up with configuration where
you have cgroup v1 and v2 enabled at the same time and the devices
controllers is enabled for cgroup v1.

In cgroup v2 there is no devices controller, the device access is
controlled using BPF and since it is not a cgroup controller both
of them can exists at the same time and both of them are applied while
resolving access to devices.

In order to avoid configuring both BPF and cgroup v1 devices we will
use BPF if possible and otherwise fallback to cgroup v1 devices.

Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
---
 src/util/vircgroup.c        | 3 ++-
 src/util/vircgroupbackend.h | 3 ++-
 src/util/vircgroupv1.c      | 9 ++++++++-
 src/util/vircgroupv2.c      | 5 ++++-
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index 4238d7014b..2ec9d28fc9 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -383,7 +383,8 @@ virCgroupDetect(virCgroupPtr group,
 
     for (i = 0; i < VIR_CGROUP_BACKEND_TYPE_LAST; i++) {
         if (group->backends[i]) {
-            int rc = group->backends[i]->detectControllers(group, controllers);
+            int rc = group->backends[i]->detectControllers(group, controllers,
+                                                           controllersAvailable);
             if (rc < 0)
                 return -1;
             controllersAvailable |= rc;
diff --git a/src/util/vircgroupbackend.h b/src/util/vircgroupbackend.h
index 24b45be9bb..9bc8e7b11d 100644
--- a/src/util/vircgroupbackend.h
+++ b/src/util/vircgroupbackend.h
@@ -96,7 +96,8 @@ typedef char *
 
 typedef int
 (*virCgroupDetectControllersCB)(virCgroupPtr group,
-                                int controllers);
+                                int controllers,
+                                int detected);
 
 typedef bool
 (*virCgroupHasControllerCB)(virCgroupPtr cgroup,
diff --git a/src/util/vircgroupv1.c b/src/util/vircgroupv1.c
index 8ce10d3608..f879c76595 100644
--- a/src/util/vircgroupv1.c
+++ b/src/util/vircgroupv1.c
@@ -420,7 +420,8 @@ virCgroupV1StealPlacement(virCgroupPtr group)
 
 static int
 virCgroupV1DetectControllers(virCgroupPtr group,
-                             int controllers)
+                             int controllers,
+                             int detected)
 {
     size_t i;
     size_t j;
@@ -430,6 +431,9 @@ virCgroupV1DetectControllers(virCgroupPtr group,
         /* First mark requested but non-existing controllers to be ignored */
         for (i = 0; i < VIR_CGROUP_CONTROLLER_LAST; i++) {
             if (((1 << i) & controllers)) {
+                int type = 1 << i;
+                if (type & detected)
+                    VIR_FREE(group->legacy[i].mountPoint);
                 /* Remove non-existent controllers  */
                 if (!group->legacy[i].mountPoint) {
                     VIR_DEBUG("Requested controller '%s' not mounted, ignoring",
@@ -469,6 +473,9 @@ virCgroupV1DetectControllers(virCgroupPtr group,
         VIR_DEBUG("Auto-detecting controllers");
         controllers = 0;
         for (i = 0; i < VIR_CGROUP_CONTROLLER_LAST; i++) {
+            int type = 1 << i;
+            if (type & detected)
+                VIR_FREE(group->legacy[i].mountPoint);
             VIR_DEBUG("Controller '%s' present=%s",
                       virCgroupV1ControllerTypeToString(i),
                       group->legacy[i].mountPoint ? "yes" : "no");
diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
index 6c851f9637..c14bdd1f6d 100644
--- a/src/util/vircgroupv2.c
+++ b/src/util/vircgroupv2.c
@@ -287,7 +287,8 @@ virCgroupV2ParseControllersFile(virCgroupPtr group)
 
 static int
 virCgroupV2DetectControllers(virCgroupPtr group,
-                             int controllers)
+                             int controllers,
+                             int detected)
 {
     size_t i;
 
@@ -300,6 +301,8 @@ virCgroupV2DetectControllers(virCgroupPtr group,
     if (virCgroupV2DevicesAvailable(group))
         group->unified.controllers |= 1 << VIR_CGROUP_CONTROLLER_DEVICES;
 
+    group->unified.controllers &= ~detected;
+
     for (i = 0; i < VIR_CGROUP_CONTROLLER_LAST; i++)
         VIR_DEBUG("Controller '%s' present=%s",
                   virCgroupV2ControllerTypeToString(i),
-- 
2.20.1