Re: [libvirt] [PATCH] qemu: Increase RLIMIT_MEMLOCK when memoryBacking/locked is used

If a domain is configured to have all its memory locked, we need to increase RLIMIT_MEMLOCK so that QEMU is actually allowed to lock the memory. --- src/qemu/qemu_command.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index c268a3a..8e2de09 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -6440,6 +6440,7 @@ qemuBuildCommandLine(virConnectPtr conn, int spice = 0; int usbcontroller = 0; bool usblegacy = false; + bool mlock; int contOrder[] = { /* We don't add an explicit IDE or FD controller because the * provided PIIX4 device already includes one. It isn't possible to @@ -6551,6 +6552,7 @@ qemuBuildCommandLine(virConnectPtr conn, virCommandAddArgFormat(cmd, "mlock=%s", def->mem.locked ? "on" : "off"); } + mlock = def->mem.locked; virCommandAddArg(cmd, "-smp"); if (!(smp = qemuBuildSmpArgStr(def, qemuCaps))) @@ -8191,22 +8193,13 @@ qemuBuildCommandLine(virConnectPtr conn, if (hostdev->source.subsys.u.pci.backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO) { - unsigned long long memKB; - if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VFIO_PCI)) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("VFIO PCI device assignment is not " "supported by this version of qemu")); goto error; } - /* VFIO requires all of the guest's memory to be - * locked resident, plus some amount for IO - * space. Alex Williamson suggested adding 1GiB for IO - * space just to be safe (some finer tuning might be - * nice, though). - */

- memKB = def->mem.max_balloon + (1024 * 1024); - virCommandSetMaxMemLock(cmd, memKB * 1024); + mlock = true; } if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) { @@ -8425,6 +8418,24 @@ qemuBuildCommandLine(virConnectPtr conn, goto error; } + if (mlock) { + unsigned long long memKB; + /* VFIO requires all of the guest's memory to be locked resident, + * plus some amount for IO space. Alex Williamson suggested + * adding 1GiB for IO space just to be safe (some finer tuning + * might be nice, though). + * + * If memory hard_limit is configured, we can use it directly as + * there is no sense to set MEMLOCK limit beyond it. Also we can + * safely use it instead of any magically computed value.

+ */ + if (def->mem.hard_limit) + memKB = def->mem.hard_limit; + else + memKB = def->mem.max_balloon + (1024 * 1024); + virCommandSetMaxMemLock(cmd, memKB * 1024); + } + virObjectUnref(cfg); return cmd;