[libvirt] [PATCH v2 1/2] conf: Disallow nonexistent NUMA nodes for hugepages

[John Ferlan]

On 09/15/2014 07:48 AM, Michal Privoznik wrote:
> As of 136ad4974 it is possible to specify different huge pages per
> guest NUMA node. However, there's no check if nodeset specified in
> ./hugepages/page contains only those guest NUMA nodes that exist.
> In other words with current code it is possible to define meaningless
> combination:
> 
>   <memoryBacking>
>     <hugepages>
>       <page size='1048576' unit='KiB' nodeset='0,2-3'/>
>       <page size='2048' unit='KiB' nodeset='1,4'/>
>     </hugepages>
>   </memoryBacking>
>   <vcpu placement='static'>4</vcpu>
>   <cpu>
>     <numa>
>       <cell id='0' cpus='0' memory='1048576'/>
>       <cell id='1' cpus='1' memory='1048576'/>
>       <cell id='2' cpus='2' memory='1048576'/>
>       <cell id='3' cpus='3' memory='1048576'/>
>     </numa>
>   </cpu>
> 
> Notice the node 4 in <hugepages/>?
> 

Coverity detected an issue with this - it's innocuous, but I wasn't sure
which way it should be handled... That is whether to add a check or
remove a check...

> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/qemu/qemu_command.c                            | 24 ++++++++++++
>  .../qemuxml2argv-hugepages-pages4.xml              | 45 ++++++++++++++++++++++
>  tests/qemuxml2argvtest.c                           |  2 +
>  3 files changed, 71 insertions(+)
>  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages4.xml
> 
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index e5270bd..1148aec 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -6542,6 +6542,30 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,
>          goto cleanup;
>      }
>  
> +    for (i = 0; i < def->mem.nhugepages; i++) {
> +        ssize_t next_bit, pos = 0;
> +
> +        if (!def->mem.hugepages[i].nodemask) {
> +            /* This is the master hugepage to use. Skip it as it has no
> +             * nodemask anyway. */
> +            continue;
> +        }
> +
> +        if (def->cpu && def->cpu->ncells) {

Because you check for def->cpu here

(16) Event cond_false: 	Condition "def->cpu", taking false branch
(18) Event var_compare_op: 	Comparing "def->cpu" to null implies that
"def->cpu" might be null.
Also see events: 	[var_deref_op]


> +            /* Fortunately, we allow only guest NUMA nodes to be continuous
> +             * starting from zero. */
> +            pos = def->cpu->ncells - 1;
> +        }
> +
> +        next_bit = virBitmapNextSetBit(def->mem.hugepages[i].nodemask, pos);
> +        if (next_bit >= 0) {
> +            virReportError(VIR_ERR_XML_DETAIL,
> +                           _("hugepages: node %zd not found"),
> +                           next_bit);
> +            goto cleanup;
> +        }
> +    }
> +
>      for (i = 0; i < def->cpu->ncells; i++) {

his makes Coverity unhappy here because it doesn't check for def->cpu first.

(23) Event var_deref_op: 	Dereferencing null pointer "def->cpu".
Also see events: 	[var_compare_op]


John
>          int cellmem = VIR_DIV_UP(def->cpu->cells[i].mem, 1024);
>          def->cpu->cells[i].mem = cellmem * 1024;
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages4.xml b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages4.xml
> new file mode 100644
> index 0000000..a3ed29b
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages4.xml
> @@ -0,0 +1,45 @@
> +<domain type='qemu'>
> +  <name>QEMUGuest1</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>4194304</memory>
> +  <currentMemory unit='KiB'>4194304</currentMemory>
> +  <memoryBacking>
> +    <hugepages>
> +      <page size='2048' unit='KiB' nodeset='1,4'/>
> +      <page size='1048576' unit='KiB' nodeset='0,2-3'/>
> +    </hugepages>
> +  </memoryBacking>
> +  <vcpu placement='static'>4</vcpu>
> +  <numatune>
> +    <memory mode='strict' nodeset='0-3'/>
> +    <memnode cellid='3' mode='strict' nodeset='3'/>
> +  </numatune>
> +  <os>
> +    <type arch='i686' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu>
> +    <numa>
> +      <cell id='0' cpus='0' memory='1048576'/>
> +      <cell id='1' cpus='1' memory='1048576'/>
> +      <cell id='2' cpus='2' memory='1048576'/>
> +      <cell id='3' cpus='3' memory='1048576'/>
> +    </numa>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +    <emulator>/usr/bin/qemu</emulator>
> +    <disk type='block' device='disk'>
> +      <source dev='/dev/HostVG/QEMUGuest1'/>
> +      <target dev='hda' bus='ide'/>
> +      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> +    </disk>
> +    <controller type='usb' index='0'/>
> +    <controller type='ide' index='0'/>
> +    <controller type='pci' index='0' model='pci-root'/>
> +    <memballoon model='virtio'/>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index 5c28253..c528499 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -684,6 +684,8 @@ mymain(void)
>              QEMU_CAPS_OBJECT_MEMORY_FILE);
>      DO_TEST("hugepages-pages3", QEMU_CAPS_MEM_PATH, QEMU_CAPS_OBJECT_MEMORY_RAM,
>              QEMU_CAPS_OBJECT_MEMORY_FILE);
> +    DO_TEST_FAILURE("hugepages-pages4", QEMU_CAPS_MEM_PATH,
> +            QEMU_CAPS_OBJECT_MEMORY_RAM, QEMU_CAPS_OBJECT_MEMORY_FILE);
>      DO_TEST("nosharepages", QEMU_CAPS_MACHINE_OPT, QEMU_CAPS_MEM_MERGE);
>      DO_TEST("disk-cdrom", NONE);
>      DO_TEST("disk-cdrom-network-http", QEMU_CAPS_KVM, QEMU_CAPS_DEVICE,
>