[libvirt] [PATCHv2 1/7] qemu: Forbid setting maximum memory size with the API with NUMA enabled

[Peter Krempa]

NUMA enabled guest configuration explicitly specifies memory sizes for
individual nodes. Allowing the virDomainSetMemoryFlags API (and friends)
to change the total doesn't make sense as the individual node configs
are not updated in that case.

Forbid use of the API in case NUMA is specified.
---

Notes:
    Version 2:
    - fixed typo in subject
    - fixed incomplete sentence in comment
    - clarified that LXC doesn't use NUMA to the extent where this change would make sense in the LXC driver

 src/qemu/qemu_driver.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index bec05d4..27cb3bf 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2307,6 +2307,16 @@ static int qemuDomainSetMemoryFlags(virDomainPtr dom, unsigned long newmem,
         if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
             /* Help clang 2.8 decipher the logic flow.  */
             sa_assert(persistentDef);
+
+            /* resizing memory with NUMA nodes specified doesn't work as there
+             * is no way to decrease the individual node sizes with this API */
+            if (virDomainNumaGetNodeCount(persistentDef->numa) > 0) {
+                virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                               _("maximum memory size of a domain with NUMA "
+                                 "nodes cannot be modified with this API"));
+                goto endjob;
+            }
+
             persistentDef->mem.max_balloon = newmem;
             if (persistentDef->mem.cur_balloon > newmem)
                 persistentDef->mem.cur_balloon = newmem;
-- 
2.2.2