[libvirt] [PATCH] qemu: Warn when using vhost-user without shared memory
When user configures vhost-user interface and forgets to also configure
any shared memory, the search for the root cause of non-operational
interface might take unpleasantly long time. Let's enhance user
experience by emitting a warning in the logs.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1266982
Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com>
---
src/qemu/qemu_process.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 420196264685..fb471342e790 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -4542,6 +4542,7 @@ qemuProcessLaunch(virConnectPtr conn,
unsigned int hostdev_flags = 0;
size_t nnicindexes = 0;
int *nicindexes = NULL;
+ bool check_shmem = false;
VIR_DEBUG("vm=%p name=%s id=%d asyncJob=%d "
"incoming.launchURI=%s incoming.deferredURI=%s "
@@ -4749,6 +4750,49 @@ qemuProcessLaunch(virConnectPtr conn,
goto cleanup;
}
+ VIR_DEBUG("Checking for any possible (non-fatal) issues");
+
+ /*
+ * For vhost-user to work, the domain has to have some type of
+ * shared memory configured. We're not the proper once to judge
+ * whether shared hugepages or shm are enough and will be in the
+ * future, so we'll just warn in case there is none of that
+ * configured. Moreover failing would give the false illusion
+ * that libvirt is really checking that everything works before
+ * running the domain and not only we are unable to do that, but
+ * it's also not our aim to do so.
+ */
+ for (i = 0; i < vm->def->nnets; i++) {
+ if (virDomainNetGetActualType(vm->def->nets[i]) ==
+ VIR_DOMAIN_NET_TYPE_VHOSTUSER) {
+ check_shmem = true;
+ break;
+ }
+ }
+
+ if (check_shmem) {
+ bool shmem = vm->def->nshmems;
+
+ /*
+ * This check is by no means complete. We merely check
+ * whetere there are *some* hugepages enabled and *some* NUMA
+ * nodes with shared memory access.
+ */
+ if (!shmem && vm->def->mem.nhugepages) {
+ for (i = 0; i < virDomainNumaGetNodeCount(vm->def->numa); i++) {
+ if (virDomainNumaGetNodeMemoryAccessMode(vm->def->numa, i) ==
+ VIR_NUMA_MEM_ACCESS_SHARED)
+ shmem = true;
+ break;
+ }
+ }
+
+ if (!shmem) {
+ VIR_WARN("Detected vhost-user interface without any shared memory.
"
+ "The interface might not be operational");
+ }
+ }
+
VIR_DEBUG("Building emulator command line");
if (!(cmd = qemuBuildCommandLine(conn, driver, vm->def, priv->monConfig,
priv->monJSON, priv->qemuCaps,
--
2.6.3