memtune: change the way how we store unlimited value

There was a mess in the way how we store unlimited value for memory
limits and how we handled values provided by user.  Internally there
were two possible ways how to store unlimited value: as 0 value or as
VIR_DOMAIN_MEMORY_PARAM_UNLIMITED.  Because we chose to store memory
limits as unsigned long long, we cannot use -1 to represent unlimited.
It's much easier for us to say that everything greater than
VIR_DOMAIN_MEMORY_PARAM_UNLIMITED means unlimited and leave 0 as valid
value despite that it makes no sense to set limit to 0.

Remove unnecessary function virCompareLimitUlong.  The update of test
is to prevent the 0 to be miss-used as unlimited in future.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1146539

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>

docs/formatdomain.html.in

@@ -798,7 +798,9 @@
         for <code>&lt;memory&gt;</code>.  For backwards
         compatibility, output is always in
         KiB.  <span class='since'><code>unit</code>
-        since 0.9.11</span></dd>
+        since 0.9.11</span>
+        Possible values for all *_limit parameters are in range from 0 to
+        VIR_DOMAIN_MEMORY_PARAM_UNLIMITED.</dd>
       <dt><code>hard_limit</code></dt>
       <dd> The optional <code>hard_limit</code> element is the maximum memory
         the guest can use. The units for this value are kibibytes (i.e. blocks

src/conf/domain_conf.c

@@ -2320,6 +2320,10 @@ virDomainDefNew(void)
     if (!(ret->numa = virDomainNumaNew()))
         goto error;
 
+    ret->mem.hard_limit = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+    ret->mem.soft_limit = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+    ret->mem.swap_hard_limit = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+
     return ret;
 
  error:
@@ -6926,6 +6930,50 @@ virDomainParseMemory(const char *xpath,
 }
 
 
+/**
+ * virDomainParseMemoryLimit:
+ *
+ * @xpath: XPath to memory amount
+ * @units_xpath: XPath to units attribute
+ * @ctxt: XPath context
+ * @mem: scaled memory amount is stored here
+ *
+ * Parse a memory element or attribute located at @xpath within @ctxt, and
+ * store the result into @mem, in blocks of 1024.  The  value is scaled by
+ * units located at @units_xpath (or the 'unit' attribute under @xpath if
+ * @units_xpath is NULL).  If units are not present, he default scale of 1024
+ * is used.  The value must not exceed VIR_DOMAIN_MEMORY_PARAM_UNLIMITED
+ * once scaled.
+ *
+ * This helper should be used only on *_limit memory elements.
+ *
+ * Return 0 on success, -1 on failure after issuing error.
+ */
+static int
+virDomainParseMemoryLimit(const char *xpath,
+                          const char *units_xpath,
+                          xmlXPathContextPtr ctxt,
+                          unsigned long long *mem)
+{
+    int ret;
+    unsigned long long bytes;
+
+    ret = virDomainParseScaledValue(xpath, units_xpath, ctxt, &bytes, 1024,
+                                    VIR_DOMAIN_MEMORY_PARAM_UNLIMITED << 10,
+                                    false);
+
+    if (ret < 0)
+        return -1;
+
+    if (ret == 0)
+        *mem = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+    else
+        *mem = virMemoryLimitTruncate(VIR_DIV_UP(bytes, 1024));
+
+    return 0;
+}
+
+
 static int
 virDomainControllerModelTypeFromString(const virDomainControllerDef *def,
                                        const char *model)
@@ -13227,20 +13275,20 @@ virDomainDefParseXML(xmlDocPtr xml,
     VIR_FREE(nodes);
 
     /* Extract other memory tunables */
-    if (virDomainParseMemory("./memtune/hard_limit[1]", NULL, ctxt,
+    if (virDomainParseMemoryLimit("./memtune/hard_limit[1]", NULL, ctxt,
-                             &def->mem.hard_limit, false, false) < 0)
+                                  &def->mem.hard_limit) < 0)
         goto error;
 
-    if (virDomainParseMemory("./memtune/soft_limit[1]", NULL, ctxt,
+    if (virDomainParseMemoryLimit("./memtune/soft_limit[1]", NULL, ctxt,
-                             &def->mem.soft_limit, false, false) < 0)
+                                  &def->mem.soft_limit) < 0)
         goto error;
 
     if (virDomainParseMemory("./memtune/min_guarantee[1]", NULL, ctxt,
                              &def->mem.min_guarantee, false, false) < 0)
         goto error;
 
-    if (virDomainParseMemory("./memtune/swap_hard_limit[1]", NULL, ctxt,
+    if (virDomainParseMemoryLimit("./memtune/swap_hard_limit[1]", NULL, ctxt,
-                             &def->mem.swap_hard_limit, false, false) < 0)
+                                  &def->mem.swap_hard_limit) < 0)
         goto error;
 
     n = virXPathULong("string(./vcpu[1])", ctxt, &count);
@@ -19809,20 +19857,17 @@ virDomainDefFormatInternal(virDomainDefPtr def,
     }
 
     /* add memtune only if there are any */
-    if ((def->mem.hard_limit &&
+    if (virMemoryLimitIsSet(def->mem.hard_limit) ||
-         def->mem.hard_limit != VIR_DOMAIN_MEMORY_PARAM_UNLIMITED) ||
+        virMemoryLimitIsSet(def->mem.soft_limit) ||
-        (def->mem.soft_limit &&
+        virMemoryLimitIsSet(def->mem.swap_hard_limit) ||
-         def->mem.soft_limit != VIR_DOMAIN_MEMORY_PARAM_UNLIMITED) ||
-        (def->mem.swap_hard_limit &&
-         def->mem.swap_hard_limit != VIR_DOMAIN_MEMORY_PARAM_UNLIMITED) ||
         def->mem.min_guarantee) {
         virBufferAddLit(buf, "<memtune>\n");
         virBufferAdjustIndent(buf, 2);
-        if (def->mem.hard_limit) {
+        if (virMemoryLimitIsSet(def->mem.hard_limit)) {
             virBufferAsprintf(buf, "<hard_limit unit='KiB'>"
                               "%llu</hard_limit>\n", def->mem.hard_limit);
         }
-        if (def->mem.soft_limit) {
+        if (virMemoryLimitIsSet(def->mem.soft_limit)) {
             virBufferAsprintf(buf, "<soft_limit unit='KiB'>"
                               "%llu</soft_limit>\n", def->mem.soft_limit);
         }
@@ -19830,7 +19875,7 @@ virDomainDefFormatInternal(virDomainDefPtr def,
             virBufferAsprintf(buf, "<min_guarantee unit='KiB'>"
                               "%llu</min_guarantee>\n", def->mem.min_guarantee);
         }
-        if (def->mem.swap_hard_limit) {
+        if (virMemoryLimitIsSet(def->mem.swap_hard_limit)) {
             virBufferAsprintf(buf, "<swap_hard_limit unit='KiB'>"
                               "%llu</swap_hard_limit>\n", def->mem.swap_hard_limit);
         }

src/libvirt-domain.c

@@ -2075,6 +2075,9 @@ virDomainSetMemoryStatsPeriod(virDomainPtr domain, int period,
  * Change all or a subset of the memory tunables.
  * This function may require privileged access to the hypervisor.
  *
+ * Possible values for all *_limit memory tunables are in range from 0 to
+ * VIR_DOMAIN_MEMORY_PARAM_UNLIMITED.
+ *
  * Returns -1 in case of error, 0 in case of success.
  */
 int

src/libvirt_private.syms

@@ -2233,7 +2233,6 @@ virUSBDeviceSetUsedBy;
 
 
 # util/virutil.h
-virCompareLimitUlong;
 virDoubleToStr;
 virEnumFromString;
 virEnumToString;

src/lxc/lxc_cgroup.c

@@ -149,17 +149,17 @@ static int virLXCCgroupSetupMemTune(virDomainDefPtr def,
     if (virCgroupSetMemory(cgroup, def->mem.max_balloon) < 0)
         goto cleanup;
 
-    if (def->mem.hard_limit &&
+    if (virMemoryLimitIsSet(def->mem.hard_limit))
-        virCgroupSetMemoryHardLimit(cgroup, def->mem.hard_limit) < 0)
+        if (virCgroupSetMemoryHardLimit(cgroup, def->mem.hard_limit) < 0)
-        goto cleanup;
+            goto cleanup;
 
-    if (def->mem.soft_limit &&
+    if (virMemoryLimitIsSet(def->mem.soft_limit))
-        virCgroupSetMemorySoftLimit(cgroup, def->mem.soft_limit) < 0)
+        if (virCgroupSetMemorySoftLimit(cgroup, def->mem.soft_limit) < 0)
-        goto cleanup;
+            goto cleanup;
 
-    if (def->mem.swap_hard_limit &&
+    if (virMemoryLimitIsSet(def->mem.swap_hard_limit))
-        virCgroupSetMemSwapHardLimit(cgroup, def->mem.swap_hard_limit) < 0)
+        if (virCgroupSetMemSwapHardLimit(cgroup, def->mem.swap_hard_limit) < 0)
-        goto cleanup;
+            goto cleanup;
 
     ret = 0;
  cleanup:

src/lxc/lxc_driver.c

@@ -874,7 +874,7 @@ lxcDomainSetMemoryParameters(virDomainPtr dom,
         if (set_hard_limit)
             mem_limit = hard_limit;
 
-        if (virCompareLimitUlong(mem_limit, swap_limit) > 0) {
+        if (mem_limit > swap_limit) {
             virReportError(VIR_ERR_INVALID_ARG, "%s",
                            _("memory hard_limit tunable value must be lower "
                              "than or equal to swap_hard_limit"));
@@ -902,7 +902,7 @@ lxcDomainSetMemoryParameters(virDomainPtr dom,
     LXC_SET_MEM_PARAMETER(virCgroupSetMemorySoftLimit, soft_limit);
 
     /* set hard limit before swap hard limit if decreasing it */
-    if (virCompareLimitUlong(vm->def->mem.hard_limit, hard_limit) > 0) {
+    if (vm->def->mem.hard_limit > hard_limit) {
         LXC_SET_MEM_PARAMETER(virCgroupSetMemoryHardLimit, hard_limit);
         /* inhibit changing the limit a second time */
         set_hard_limit = false;
@@ -983,7 +983,6 @@ lxcDomainGetMemoryParameters(virDomainPtr dom,
         case 0: /* fill memory hard limit here */
             if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
                 val = vmdef->mem.hard_limit;
-                val = val ? val : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
             } else if (virCgroupGetMemoryHardLimit(priv->cgroup, &val) < 0) {
                 goto cleanup;
             }
@@ -994,7 +993,6 @@ lxcDomainGetMemoryParameters(virDomainPtr dom,
         case 1: /* fill memory soft limit here */
             if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
                 val = vmdef->mem.soft_limit;
-                val = val ? val : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
             } else if (virCgroupGetMemorySoftLimit(priv->cgroup, &val) < 0) {
                 goto cleanup;
             }
@@ -1005,7 +1003,6 @@ lxcDomainGetMemoryParameters(virDomainPtr dom,
         case 2: /* fill swap hard limit here */
             if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
                 val = vmdef->mem.swap_hard_limit;
-                val = val ? val : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
             } else if (virCgroupGetMemSwapHardLimit(priv->cgroup, &val) < 0) {
                 goto cleanup;
             }

src/lxc/lxc_fuse.c

@@ -165,11 +165,13 @@ static int lxcProcReadMeminfo(char *hostpath, virDomainDefPtr def,
             *ptr = '\0';
 
             if (STREQ(line, "MemTotal") &&
-                (def->mem.hard_limit || def->mem.max_balloon)) {
+                (virMemoryLimitIsSet(def->mem.hard_limit) ||
+                 def->mem.max_balloon)) {
                 virBufferAsprintf(new_meminfo, "MemTotal:       %8llu kB\n",
                                   meminfo.memtotal);
             } else if (STREQ(line, "MemFree") &&
-                       (def->mem.hard_limit || def->mem.max_balloon)) {
+                       (virMemoryLimitIsSet(def->mem.hard_limit) ||
+                        def->mem.max_balloon)) {
                 virBufferAsprintf(new_meminfo, "MemFree:        %8llu kB\n",
                                   (meminfo.memtotal - meminfo.memusage));
             } else if (STREQ(line, "Buffers")) {
@@ -198,10 +200,12 @@ static int lxcProcReadMeminfo(char *hostpath, virDomainDefPtr def,
             } else if (STREQ(line, "Unevictable")) {
                 virBufferAsprintf(new_meminfo, "Unevictable:    %8llu kB\n",
                                   meminfo.unevictable);
-            } else if (STREQ(line, "SwapTotal") && def->mem.swap_hard_limit) {
+            } else if (STREQ(line, "SwapTotal") &&
+                       virMemoryLimitIsSet(def->mem.swap_hard_limit)) {
                 virBufferAsprintf(new_meminfo, "SwapTotal:      %8llu kB\n",
                                   (meminfo.swaptotal - meminfo.memtotal));
-            } else if (STREQ(line, "SwapFree") && def->mem.swap_hard_limit) {
+            } else if (STREQ(line, "SwapFree") &&
+                       virMemoryLimitIsSet(def->mem.swap_hard_limit)) {
                 virBufferAsprintf(new_meminfo, "SwapFree:       %8llu kB\n",
                                   (meminfo.swaptotal - meminfo.memtotal -
                                    meminfo.swapusage + meminfo.memusage));

src/lxc/lxc_native.c

@@ -773,7 +773,7 @@ lxcSetMemTune(virDomainDefPtr def, virConfPtr properties)
             return -1;
         size = size / 1024;
         def->mem.max_balloon = size;
-        def->mem.hard_limit = size;
+        def->mem.hard_limit = virMemoryLimitTruncate(size);
     }
 
     if ((value = virConfGetValue(properties,
@@ -782,7 +782,7 @@ lxcSetMemTune(virDomainDefPtr def, virConfPtr properties)
         if (lxcConvertSize(value->str, &size) < 0)
             return -1;
 
-        def->mem.soft_limit = size / 1024;
+        def->mem.soft_limit = virMemoryLimitTruncate(size / 1024);
     }
 
     if ((value = virConfGetValue(properties,
@@ -791,7 +791,7 @@ lxcSetMemTune(virDomainDefPtr def, virConfPtr properties)
         if (lxcConvertSize(value->str, &size) < 0)
             return -1;
 
-       def->mem.swap_hard_limit = size / 1024;
+        def->mem.swap_hard_limit = virMemoryLimitTruncate(size / 1024);
     }
     return 0;
 }

src/openvz/openvz_conf.c

@@ -479,12 +479,12 @@ openvzReadMemConf(virDomainDefPtr def, int veid)
             goto error;
         }
         if (barrier == LONG_MAX)
-            def->mem.soft_limit = 0ull;
+            def->mem.soft_limit = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
         else
             def->mem.soft_limit = barrier * kb_per_pages;
 
         if (limit == LONG_MAX)
-            def->mem.hard_limit = 0ull;
+            def->mem.hard_limit = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
         else
             def->mem.hard_limit = limit * kb_per_pages;
     }

src/openvz/openvz_driver.c

@@ -1850,7 +1850,7 @@ openvzDomainGetMemoryParameters(virDomainPtr domain,
             if (openvzDomainGetBarrierLimit(domain, name, &barrier, &limit) < 0)
                 goto cleanup;
 
-            val = (limit == LONG_MAX) ? 0ull : limit * kb_per_pages;
+            val = (limit == LONG_MAX) ? VIR_DOMAIN_MEMORY_PARAM_UNLIMITED : limit * kb_per_pages;
             if (virTypedParameterAssign(param, VIR_DOMAIN_MEMORY_HARD_LIMIT,
                                         VIR_TYPED_PARAM_ULLONG, val) < 0)
                 goto cleanup;
@@ -1861,7 +1861,7 @@ openvzDomainGetMemoryParameters(virDomainPtr domain,
             if (openvzDomainGetBarrierLimit(domain, name, &barrier, &limit) < 0)
                 goto cleanup;
 
-            val = (barrier == LONG_MAX) ? 0ull : barrier * kb_per_pages;
+            val = (barrier == LONG_MAX) ? VIR_DOMAIN_MEMORY_PARAM_UNLIMITED : barrier * kb_per_pages;
             if (virTypedParameterAssign(param, VIR_DOMAIN_MEMORY_SOFT_LIMIT,
                                         VIR_TYPED_PARAM_ULLONG, val) < 0)
                 goto cleanup;

src/qemu/qemu_cgroup.c

@@ -471,9 +471,9 @@ qemuSetupMemoryCgroup(virDomainObjPtr vm)
     qemuDomainObjPrivatePtr priv = vm->privateData;
 
     if (!virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_MEMORY)) {
-        if (vm->def->mem.hard_limit != 0 ||
+        if (virMemoryLimitIsSet(vm->def->mem.hard_limit) ||
-            vm->def->mem.soft_limit != 0 ||
+            virMemoryLimitIsSet(vm->def->mem.soft_limit) ||
-            vm->def->mem.swap_hard_limit != 0) {
+            virMemoryLimitIsSet(vm->def->mem.swap_hard_limit)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("Memory cgroup is not available on this host"));
             return -1;
@@ -482,17 +482,17 @@ qemuSetupMemoryCgroup(virDomainObjPtr vm)
         }
     }
 
-    if (vm->def->mem.hard_limit != 0 &&
+    if (virMemoryLimitIsSet(vm->def->mem.hard_limit))
-        virCgroupSetMemoryHardLimit(priv->cgroup, vm->def->mem.hard_limit) < 0)
+        if (virCgroupSetMemoryHardLimit(priv->cgroup, vm->def->mem.hard_limit) < 0)
-        return -1;
+            return -1;
 
-    if (vm->def->mem.soft_limit != 0 &&
+    if (virMemoryLimitIsSet(vm->def->mem.soft_limit))
-        virCgroupSetMemorySoftLimit(priv->cgroup, vm->def->mem.soft_limit) < 0)
+        if (virCgroupSetMemorySoftLimit(priv->cgroup, vm->def->mem.soft_limit) < 0)
-        return -1;
+            return -1;
 
-    if (vm->def->mem.swap_hard_limit != 0 &&
+    if (virMemoryLimitIsSet(vm->def->mem.swap_hard_limit))
-        virCgroupSetMemSwapHardLimit(priv->cgroup, vm->def->mem.swap_hard_limit) < 0)
+        if (virCgroupSetMemSwapHardLimit(priv->cgroup, vm->def->mem.swap_hard_limit) < 0)
-        return -1;
+            return -1;
 
     return 0;
 }

src/qemu/qemu_command.c

@@ -8409,8 +8409,10 @@ qemuBuildCommandLine(virConnectPtr conn,
         /* If we have no cgroups then we can have no tunings that
          * require them */
 
-        if (def->mem.hard_limit || def->mem.soft_limit ||
+        if (virMemoryLimitIsSet(def->mem.hard_limit) ||
-            def->mem.min_guarantee || def->mem.swap_hard_limit) {
+            virMemoryLimitIsSet(def->mem.soft_limit) ||
+            def->mem.min_guarantee ||
+            virMemoryLimitIsSet(def->mem.swap_hard_limit)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("Memory tuning is not available in session mode"));
             goto error;
@@ -10483,7 +10485,7 @@ qemuBuildCommandLine(virConnectPtr conn,
          * space just to be safe (some finer tuning might be
          * nice, though).
          */
-        memKB = def->mem.hard_limit ?
+        memKB = virMemoryLimitIsSet(def->mem.hard_limit) ?
             def->mem.hard_limit : def->mem.max_balloon + 1024 * 1024;
         virCommandSetMaxMemLock(cmd, memKB * 1024);
     }

src/qemu/qemu_driver.c

@@ -9143,8 +9143,7 @@ qemuDomainSetMemoryParameters(virDomainPtr dom,
 
 #undef VIR_GET_LIMIT_PARAMETER
 
-    /* Swap hard limit must be greater than hard limit.
+    /* Swap hard limit must be greater than hard limit. */
-     * Note that limit of 0 denotes unlimited */
     if (set_swap_hard_limit || set_hard_limit) {
         unsigned long long mem_limit = vm->def->mem.hard_limit;
         unsigned long long swap_limit = vm->def->mem.swap_hard_limit;
@@ -9155,7 +9154,7 @@ qemuDomainSetMemoryParameters(virDomainPtr dom,
         if (set_hard_limit)
             mem_limit = hard_limit;
 
-        if (virCompareLimitUlong(mem_limit, swap_limit) > 0) {
+        if (mem_limit > swap_limit) {
             virReportError(VIR_ERR_INVALID_ARG, "%s",
                            _("memory hard_limit tunable value must be lower "
                              "than or equal to swap_hard_limit"));
@@ -9183,7 +9182,7 @@ qemuDomainSetMemoryParameters(virDomainPtr dom,
     QEMU_SET_MEM_PARAMETER(virCgroupSetMemorySoftLimit, soft_limit);
 
     /* set hard limit before swap hard limit if decreasing it */
-    if (virCompareLimitUlong(vm->def->mem.hard_limit, hard_limit) > 0) {
+    if (vm->def->mem.hard_limit > hard_limit) {
         QEMU_SET_MEM_PARAMETER(virCgroupSetMemoryHardLimit, hard_limit);
         /* inhibit changing the limit a second time */
         set_hard_limit = false;
@@ -9279,7 +9278,6 @@ qemuDomainGetMemoryParameters(virDomainPtr dom,
             switch (i) {
             case 0: /* fill memory hard limit here */
                 value = persistentDef->mem.hard_limit;
-                value = value ? value : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
                 if (virTypedParameterAssign(param, VIR_DOMAIN_MEMORY_HARD_LIMIT,
                                             VIR_TYPED_PARAM_ULLONG, value) < 0)
                     goto cleanup;
@@ -9287,7 +9285,6 @@ qemuDomainGetMemoryParameters(virDomainPtr dom,
 
             case 1: /* fill memory soft limit here */
                 value = persistentDef->mem.soft_limit;
-                value = value ? value : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
                 if (virTypedParameterAssign(param, VIR_DOMAIN_MEMORY_SOFT_LIMIT,
                                             VIR_TYPED_PARAM_ULLONG, value) < 0)
                     goto cleanup;
@@ -9295,7 +9292,6 @@ qemuDomainGetMemoryParameters(virDomainPtr dom,
 
             case 2: /* fill swap hard limit here */
                 value = persistentDef->mem.swap_hard_limit;
-                value = value ? value : VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
                 if (virTypedParameterAssign(param, VIR_DOMAIN_MEMORY_SWAP_HARD_LIMIT,
                                             VIR_TYPED_PARAM_ULLONG, value) < 0)
                     goto cleanup;

src/qemu/qemu_hotplug.c

@@ -1250,7 +1250,7 @@ qemuDomainAttachHostPCIDevice(virQEMUDriverPtr driver,
          * Kibibytes, but virProcessSetMaxMemLock expects the value in
          * bytes.
          */
-        memKB = vm->def->mem.hard_limit
+        memKB = virMemoryLimitIsSet(vm->def->mem.hard_limit)
             ? vm->def->mem.hard_limit
             : vm->def->mem.max_balloon + (1024 * 1024);
         virProcessSetMaxMemLock(vm->pid, memKB * 1024);

src/qemu/qemu_migration.c

@@ -2986,7 +2986,8 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver,
                                        QEMU_MIGRATION_COOKIE_NBD)))
         goto cleanup;
 
-    if (STREQ_NULLABLE(protocol, "rdma") && !vm->def->mem.hard_limit) {
+    if (STREQ_NULLABLE(protocol, "rdma") &&
+        !virMemoryLimitIsSet(vm->def->mem.hard_limit)) {
         virReportError(VIR_ERR_OPERATION_INVALID, "%s",
                        _("cannot start RDMA migration with no memory hard "
                          "limit set"));
@@ -4102,7 +4103,7 @@ static int doNativeMigrate(virQEMUDriverPtr driver,
                              "with this QEMU binary"));
             goto cleanup;
         }
-        if (!vm->def->mem.hard_limit) {
+        if (!virMemoryLimitIsSet(vm->def->mem.hard_limit)) {
             virReportError(VIR_ERR_OPERATION_INVALID, "%s",
                            _("cannot start RDMA migration with no memory hard "
                              "limit set"));

src/util/virutil.c

@@ -2364,29 +2364,6 @@ virFindFCHostCapableVport(const char *sysfs_prefix ATTRIBUTE_UNUSED)
 
 #endif /* __linux__ */
 
-/**
- * virCompareLimitUlong:
- *
- * Compare two unsigned long long numbers. Value '0' of the arguments has a
- * special meaning of 'unlimited' and thus greater than any other value.
- *
- * Returns 0 if the numbers are equal, -1 if b is greater, 1 if a is greater.
- */
-int
-virCompareLimitUlong(unsigned long long a, unsigned long long b)
-{
-    if (a == b)
-        return 0;
-
-    if (!b)
-        return -1;
-
-    if (a == 0 || a > b)
-        return 1;
-
-    return -1;
-}
-
 /**
  * virParseOwnershipIds:
  *

src/util/virutil.h

@@ -210,8 +210,6 @@ char *virGetFCHostNameByWWN(const char *sysfs_prefix,
 
 char *virFindFCHostCapableVport(const char *sysfs_prefix);
 
-int virCompareLimitUlong(unsigned long long a, unsigned long long b);
-
 int virParseOwnershipIds(const char *label, uid_t *uidPtr, gid_t *gidPtr);
 
 const char *virGetEnvBlockSUID(const char *name);

tests/qemuxml2argvdata/qemuxml2argv-memtune.xml

@@ -5,7 +5,7 @@
   <currentMemory unit='KiB'>219136</currentMemory>
   <memtune>
     <hard_limit unit='KiB'>512000</hard_limit>
-    <soft_limit unit='bytes'>131071999</soft_limit>
+    <soft_limit unit='bytes'>0</soft_limit>
     <swap_hard_limit unit='KB'>1048576</swap_hard_limit>
   </memtune>
   <vcpu placement='static'>1</vcpu>

tests/qemuxml2xmloutdata/qemuxml2xmlout-memtune.xml

@@ -5,7 +5,7 @@
   <currentMemory unit='KiB'>219136</currentMemory>
   <memtune>
     <hard_limit unit='KiB'>512000</hard_limit>
-    <soft_limit unit='KiB'>128000</soft_limit>
+    <soft_limit unit='KiB'>0</soft_limit>
     <swap_hard_limit unit='KiB'>1024000</swap_hard_limit>
   </memtune>
   <vcpu placement='static'>1</vcpu>