[libvirt] [PATCH v2] qemu: Forbid <memoryBacking><locked> without <memtune><hard_limit>

In order for memory locking to work, the hard limit on memory locking (and usage) has to be set appropriately by the user. The documentation mentions the requirement already: with this patch, it's going to be enforced by runtime checks as well, by forbidding a non-compliant guest from starting at all. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1316774 --- Changes from [v1] * Address review feeback: - check in BuildCommandLine rather than in PostParse, so that non-compliant guests will merely fail to start rather than disappear completely. [v1] https://www.redhat.com/archives/libvir-list/2017-February/msg00180.html src/qemu/qemu_command.c | 9 +++++++++ tests/qemuxml2argvdata/qemuxml2argv-mlock-on.xml | 3 +++ 2 files changed, 12 insertions(+) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 1396661..ca3bcdc 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7340,6 +7340,15 @@ qemuBuildMemCommandLine(virCommandPtr cmd, qemuBuildMemPathStr(cfg, def, qemuCaps, cmd) < 0) return -1; + /* Memory locking can only work properly if the memory locking limit + * for the QEMU process has been raised appropriately: the default one + * is extrememly low, so there's no way the guest will fit in there */ + if (def->mem.locked && !virMemoryLimitIsSet(def->mem.hard_limit)) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("Setting <memoryBacking><locked> requires " + "<memtune><hard_limit> to be set as well")); + return -1; + } if (def->mem.locked && !virQEMUCapsGet(qemuCaps, QEMU_CAPS_REALTIME_MLOCK)) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("memory locking not supported by QEMU binary")); diff --git a/tests/qemuxml2argvdata/qemuxml2argv-mlock-on.xml b/tests/qemuxml2argvdata/qemuxml2argv-mlock-on.xml index 20a5eaa..2046663 100644 --- a/tests/qemuxml2argvdata/qemuxml2argv-mlock-on.xml +++ b/tests/qemuxml2argvdata/qemuxml2argv-mlock-on.xml @@ -3,6 +3,9 @@ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid> <memory unit='KiB'>219136</memory> <currentMemory unit='KiB'>219136</currentMemory> + <memtune> + <hard_limit unit='KiB'>256000</hard_limit> + </memtune> <memoryBacking> <locked/> </memoryBacking> -- 2.7.4