Added capability checking for block <iotune> setting.

There was missing capability for blkiotune and thus specifying these
settings caused libvirt to run qemu with invalid parameters and then
reporting qemu error instead of the standard libvirt one. The support
for blkiotune setting was added in upstream qemu repo under commit
0563e191516289c9d2f282a8c50f2eecef2fa773.

src/qemu/qemu_capabilities.c

@@ -150,6 +150,8 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
               "drive-copy-on-read",
               "cpu-host",
               "fsdev-writeout",
+
+              "drive-iotune", /* 85 */
     );
 
 struct qemu_feature_flags {
@@ -1031,6 +1033,8 @@ qemuCapsComputeCmdFlags(const char *help,
             qemuCapsSet(flags, QEMU_CAPS_DRIVE_AIO);
         if (strstr(help, "copy-on-read=on|off"))
             qemuCapsSet(flags, QEMU_CAPS_DRIVE_COPY_ON_READ);
+        if (strstr(help, "bps="))
+            qemuCapsSet(flags, QEMU_CAPS_DRIVE_IOTUNE);
     }
     if ((p = strstr(help, "-vga")) && !strstr(help, "-std-vga")) {
         const char *nl = strstr(p, "\n");

src/qemu/qemu_capabilities.h

@@ -124,6 +124,8 @@ enum qemuCapsFlags {
     QEMU_CAPS_CPU_HOST          = 83, /* support for -cpu host */
     QEMU_CAPS_FSDEV_WRITEOUT     = 84, /* -fsdev writeout supported */
 
+    QEMU_CAPS_DRIVE_IOTUNE       = 85, /* -drive bps= and friends ({b,io}ps{_rd,_wr,}) */
+
     QEMU_CAPS_LAST,                   /* this must always be the last item */
 };
 

src/qemu/qemu_command.c

@@ -1987,6 +1987,19 @@ qemuBuildDriveStr(virConnectPtr conn ATTRIBUTE_UNUSED,
     }
 
     /* block I/O throttling */
+    if ((disk->blkdeviotune.total_bytes_sec ||
+         disk->blkdeviotune.read_bytes_sec ||
+         disk->blkdeviotune.write_bytes_sec ||
+         disk->blkdeviotune.total_iops_sec ||
+         disk->blkdeviotune.read_iops_sec ||
+         disk->blkdeviotune.write_iops_sec) &&
+        !qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_IOTUNE)) {
+        qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                        _("block I/O throttling not supported with this "
+                          "QEMU binary"));
+        goto error;
+    }
+
     if (disk->blkdeviotune.total_bytes_sec) {
         virBufferAsprintf(&opt, ",bps=%llu",
                           disk->blkdeviotune.total_bytes_sec);

tests/qemuxml2argvtest.c

@@ -705,7 +705,7 @@ mymain(void)
     DO_TEST("cputune", false, QEMU_CAPS_NAME);
     DO_TEST("numatune-memory", false, NONE);
     DO_TEST("blkdeviotune", false, QEMU_CAPS_NAME, QEMU_CAPS_DEVICE,
-            QEMU_CAPS_DRIVE);
+            QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_IOTUNE);
 
     DO_TEST("multifunction-pci-device", false,
             QEMU_CAPS_DRIVE, QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG,