From 38db498e14eb27481b3f46cacff84a394c86f96c Mon Sep 17 00:00:00 2001 From: David Gibson Date: Fri, 24 Jul 2015 05:26:20 +0200 Subject: [PATCH 58/58] spapr: Don't allow memory hotplug to memory less nodes Message-id: <1437715580-14817-29-git-send-email-dgibson@redhat.com> Patchwork-id: 67145 O-Subject: [RHEL7.2 qemu-kvm-rhev PATCHv3 28/28] spapr: Don't allow memory hotplug to memory less nodes Bugzilla: 1211117 RH-Acked-by: Laurent Vivier RH-Acked-by: Igor Mammedov RH-Acked-by: Laszlo Ersek Currently PowerPC kernel doesn't allow hot-adding memory to memory-less node, but instead will silently add the memory to the first node that has some memory. This causes two unexpected behaviours for the user. - Memory gets hotplugged to a different node than what the user specified. - Since pc-dimm subsystem in QEMU still thinks that memory belongs to memory-less node, a reboot will set things accordingly and the previously hotplugged memory now ends in the right node. This appears as if some memory moved from one node to another. So until kernel starts supporting memory hotplug to memory-less nodes, just prevent such attempts upfront in QEMU. Signed-off-by: Bharata B Rao Reviewed-by: David Gibson Signed-off-by: David Gibson (cherry picked from commit 5e9b41601916a92bb2253b0c5332266776d6bbf2) Signed-off-by: David Gibson Signed-off-by: Miroslav Rezanina --- hw/ppc/spapr.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 27b6dde..8beaac3 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -2125,7 +2125,7 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev, sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine()); if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) { - uint32_t node; + int node; if (!smc->dr_lmb_enabled) { error_setg(errp, "Memory hotplug not supported for this machine"); @@ -2136,6 +2136,28 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev, return; } + /* + * Currently PowerPC kernel doesn't allow hot-adding memory to + * memory-less node, but instead will silently add the memory + * to the first node that has some memory. This causes two + * unexpected behaviours for the user. + * + * - Memory gets hotplugged to a different node than what the user + * specified. + * - Since pc-dimm subsystem in QEMU still thinks that memory belongs + * to memory-less node, a reboot will set things accordingly + * and the previously hotplugged memory now ends in the right node. + * This appears as if some memory moved from one node to another. + * + * So until kernel starts supporting memory hotplug to memory-less + * nodes, just prevent such attempts upfront in QEMU. + */ + if (nb_numa_nodes && !numa_info[node].node_mem) { + error_setg(errp, "Can't hotplug memory to memory-less node %d", + node); + return; + } + spapr_memory_plug(hotplug_dev, dev, node, errp); } } -- 1.8.3.1