[PATCH 7/8] qemu: Discard caps cache when KVM availability changes

[Jiri Denemark <jdenemar@xxxxxxxxxx>]

Since CPU capabilities depend on accelerator used when probing QEMU the
cache becomes invalid when KVM becomes available or if it is not
available anymore.

Signed-off-by: Jiri Denemark <jdenemar@xxxxxxxxxx>
---
 src/qemu/qemu_capabilities.c | 37 ++++++++++++++++++++++++++++++++-----
 src/qemu/qemu_capabilities.h |  4 +++-
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index d1c31ad..9fe4363 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -3469,7 +3469,9 @@ virQEMUCapsReset(virQEMUCapsPtr qemuCaps)
 static int
 virQEMUCapsInitCached(virCapsPtr caps,
                       virQEMUCapsPtr qemuCaps,
-                      const char *cacheDir)
+                      const char *cacheDir,
+                      uid_t runUid,
+                      gid_t runGid)
 {
     char *capsdir = NULL;
     char *capsfile = NULL;
@@ -3519,7 +3521,7 @@ virQEMUCapsInitCached(virCapsPtr caps,
         goto discard;
     }
 
-    if (!virQEMUCapsIsValid(qemuCaps, qemuctime))
+    if (!virQEMUCapsIsValid(qemuCaps, qemuctime, runUid, runGid))
         goto discard;
 
     /* Discard cache if QEMU binary or libvirtd changed */
@@ -4067,7 +4069,8 @@ virQEMUCapsNewForBinaryInternal(virCapsPtr caps,
 
     if (!cacheDir)
         rv = 0;
-    else if ((rv = virQEMUCapsInitCached(caps, qemuCaps, cacheDir)) < 0)
+    else if ((rv = virQEMUCapsInitCached(caps, qemuCaps, cacheDir,
+                                         runUid, runGid)) < 0)
         goto error;
 
     if (rv == 0) {
@@ -4115,8 +4118,12 @@ virQEMUCapsNewForBinary(virCapsPtr caps,
 
 bool
 virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps,
-                   time_t ctime)
+                   time_t ctime,
+                   uid_t runUid,
+                   gid_t runGid)
 {
+    bool kvmUsable;
+
     if (!qemuCaps->binary)
         return true;
 
@@ -4142,6 +4149,26 @@ virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps,
         return false;
     }
 
+    kvmUsable = virFileAccessibleAs("/dev/kvm", R_OK | W_OK,
+                                    runUid, runGid) == 0;
+
+    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_KVM) &&
+        virQEMUCapsGet(qemuCaps, QEMU_CAPS_ENABLE_KVM) &&
+        kvmUsable) {
+        VIR_DEBUG("Dropping cached capabilities for '%s': KVM was not "
+                  "enabled when probing, but it should be usable now",
+                  qemuCaps->binary);
+        return false;
+    }
+
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_KVM) &&
+        !kvmUsable) {
+        VIR_DEBUG("Dropping cached capabilities for '%s': KVM was enabled "
+                  "when probing, but it is not available now",
+                  qemuCaps->binary);
+        return false;
+    }
+
     return true;
 }
 
@@ -4235,7 +4262,7 @@ virQEMUCapsCacheLookup(virCapsPtr caps,
     virMutexLock(&cache->lock);
     ret = virHashLookup(cache->binaries, binary);
     if (ret &&
-        !virQEMUCapsIsValid(ret, 0)) {
+        !virQEMUCapsIsValid(ret, 0, cache->runUid, cache->runGid)) {
         VIR_DEBUG("Cached capabilities %p no longer valid for %s",
                   ret, binary);
         virHashRemoveEntry(cache->binaries, binary);
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 6c45a67..5310416 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -450,7 +450,9 @@ int virQEMUCapsGetMachineTypesCaps(virQEMUCapsPtr qemuCaps,
                                    virCapsGuestMachinePtr **machines);
 
 bool virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps,
-                        time_t ctime);
+                        time_t ctime,
+                        uid_t runUid,
+                        gid_t runGid);
 
 void virQEMUCapsFilterByMachineType(virQEMUCapsPtr qemuCaps,
                                     const char *machineType);
-- 
2.10.2

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