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qemu: Warn when using vhost-user without shared memory

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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@redhat.com>
This commit is contained in:
Martin Kletzander 2015-12-08 14:15:47 +01:00
parent ec93cc25ec
commit 686eb7a24f
1 changed files with 44 additions and 0 deletions
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44
src/qemu/qemu_process.c
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@ -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 ones to judge
* whether shared hugepages or shm are enough and will be in the
* future, so we'll just warn in case neither is 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
* whether 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,