qemu_domain: add a PPC64 memLockLimit helper

There is a lot of documentation in the comments about how PPC64 handles
passthrough VFIO devices to calculate the @memLockLimit. And more will
be added with the PPC64 NVLink2 support code.

Let's remove the PPC64 code from qemuDomainGetMemLockLimitBytes()
body and put it into a helper function. This will simplify the
flow of qemuDomainGetMemLockLimitBytes() that handles all the other
platforms and improves readability of the PPC64 specifics.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/qemu/qemu_domain.c

@@ -10344,42 +10344,21 @@ qemuDomainUpdateCurrentMemorySize(virDomainObjPtr vm)
 
 
 /**
- * qemuDomainGetMemLockLimitBytes:
+ * getPPC64MemLockLimitBytes:
  * @def: domain definition
  *
- * Calculate the memory locking limit that needs to be set in order for
+ * A PPC64 helper that calculates the memory locking limit in order for
- * the guest to operate properly. The limit depends on a number of factors,
+ * the guest to operate properly.
- * including certain configuration options and less immediately apparent ones
- * such as the guest architecture or the use of certain devices.
- *
- * Returns: the memory locking limit, or 0 if setting the limit is not needed
  */
-unsigned long long
+static unsigned long long
-qemuDomainGetMemLockLimitBytes(virDomainDefPtr def)
+getPPC64MemLockLimitBytes(virDomainDefPtr def)
 {
     unsigned long long memKB = 0;
-    size_t i;
+    unsigned long long baseLimit = 0;
-
+    unsigned long long memory = 0;
-    /* prefer the hard limit */
+    unsigned long long maxMemory = 0;
-    if (virMemoryLimitIsSet(def->mem.hard_limit)) {
-        memKB = def->mem.hard_limit;
-        goto done;
-    }
-
-    /* If the guest wants its memory to be locked, we need to raise the memory
-     * locking limit so that the OS will not refuse allocation requests;
-     * however, there is no reliable way for us to figure out how much memory
-     * the QEMU process will allocate for its own use, so our only way out is
-     * to remove the limit altogether. Use with extreme care */
-    if (def->mem.locked)
-        return VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
-
-    if (ARCH_IS_PPC64(def->os.arch) && def->virtType == VIR_DOMAIN_VIRT_KVM) {
-        unsigned long long maxMemory;
-        unsigned long long memory;
-        unsigned long long baseLimit;
     unsigned long long passthroughLimit = 0;
-        size_t nPCIHostBridges = 0;
+    size_t i, nPCIHostBridges = 0;
     bool usesVFIO = false;
 
     for (i = 0; i < def->ncontrollers; i++) {
@@ -10450,9 +10429,45 @@ qemuDomainGetMemLockLimitBytes(virDomainDefPtr def)
                                memory / 512 * nPCIHostBridges + 8192);
 
     memKB = baseLimit + passthroughLimit;
+
+    return memKB << 10;
+}
+
+
+/**
+ * qemuDomainGetMemLockLimitBytes:
+ * @def: domain definition
+ *
+ * Calculate the memory locking limit that needs to be set in order for
+ * the guest to operate properly. The limit depends on a number of factors,
+ * including certain configuration options and less immediately apparent ones
+ * such as the guest architecture or the use of certain devices.
+ *
+ * Returns: the memory locking limit, or 0 if setting the limit is not needed
+ */
+unsigned long long
+qemuDomainGetMemLockLimitBytes(virDomainDefPtr def)
+{
+    unsigned long long memKB = 0;
+    size_t i;
+
+    /* prefer the hard limit */
+    if (virMemoryLimitIsSet(def->mem.hard_limit)) {
+        memKB = def->mem.hard_limit;
         goto done;
     }
 
+    /* If the guest wants its memory to be locked, we need to raise the memory
+     * locking limit so that the OS will not refuse allocation requests;
+     * however, there is no reliable way for us to figure out how much memory
+     * the QEMU process will allocate for its own use, so our only way out is
+     * to remove the limit altogether. Use with extreme care */
+    if (def->mem.locked)
+        return VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+
+    if (ARCH_IS_PPC64(def->os.arch) && def->virtType == VIR_DOMAIN_VIRT_KVM)
+        return getPPC64MemLockLimitBytes(def);
+
     /* For device passthrough using VFIO the guest memory and MMIO memory
      * regions need to be locked persistent in order to allow DMA.
      *