Add standard constants for CPU architectures

Introduce a nova/compute/arch.py module to serve a similar role
to nova/compute/vmmode.py, by providing constants for known
CPU architectures and validation/canonicalization APIs

Related-bug: #1348624
Change-Id: Idd4907b5488dd0832c15783d87d57d77ae654519

nova/compute/arch.py

@@ -0,0 +1,155 @@
+# Copyright 2014 Red Hat, Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Constants and helper APIs for dealing with CPU architectures
+
+The constants provide the standard names for all known processor
+architectures. Many have multiple variants to deal with big-endian
+vs little-endian modes, as well as 32 vs 64 bit word sizes. These
+names are chosen to be identical to the architecture names expected
+by libvirt, so if ever adding new ones, ensure it matches libvirt's
+expectation.
+"""
+
+import os
+
+from nova import exception
+
+ALPHA = "alpha"
+ARMV6 = "armv6"
+ARMV7 = "armv7l"
+ARMV7B = "armv7b"
+
+AARCH64 = "aarch64"
+CRIS = "cris"
+I686 = "i686"
+IA64 = "ia64"
+LM32 = "lm32"
+
+M68K = "m68k"
+MICROBLAZE = "microblaze"
+MICROBLAZEEL = "microblazeel"
+MIPS = "mips"
+MIPSEL = "mipsel"
+
+MIPS64 = "mips64"
+MIPS64EL = "mips64el"
+OPENRISC = "openrisc"
+PARISC = "parisc"
+PARISC64 = "parisc64"
+
+PPC = "ppc"
+PPCLE = "ppcle"
+PPC64 = "ppc64"
+PPC64LE = "ppc64le"
+PPCEMB = "ppcemb"
+
+S390 = "s390"
+S390X = "s390x"
+SH4 = "sh4"
+SH4EB = "sh4eb"
+SPARC = "sparc"
+
+SPARC64 = "sparc64"
+UNICORE32 = "unicore32"
+X86_64 = "x86_64"
+XTENSA = "xtensa"
+XTENSAEB = "xtensaeb"
+
+
+ALL = [
+    ALPHA,
+    ARMV6,
+    ARMV7,
+    ARMV7B,
+
+    AARCH64,
+    CRIS,
+    I686,
+    IA64,
+    LM32,
+
+    M68K,
+    MICROBLAZE,
+    MICROBLAZEEL,
+    MIPS,
+    MIPSEL,
+
+    MIPS64,
+    MIPS64EL,
+    OPENRISC,
+    PARISC,
+    PARISC64,
+
+    PPC,
+    PPCLE,
+    PPC64,
+    PPC64LE,
+    PPCEMB,
+
+    S390,
+    S390X,
+    SH4,
+    SH4EB,
+    SPARC,
+
+    SPARC64,
+    UNICORE32,
+    X86_64,
+    XTENSA,
+    XTENSAEB,
+]
+
+
+def from_host():
+    """Get the architecture of the host OS
+
+    :returns: the canonicalized host architecture
+    """
+
+    return canonicalize(os.uname()[4])
+
+
+def is_valid(name):
+    """Check if a string is a valid architecture
+
+    :param name: architecture name to validate
+
+    :returns: True if @name is valid
+    """
+
+    return name in ALL
+
+
+def canonicalize(name):
+    """Canonicalize the architecture name
+
+    :param name: architecture name to canonicalize
+
+    :returns: a canonical architecture name
+    """
+
+    if name is None:
+        return None
+
+    newname = name.lower()
+
+    if newname in ("i386", "i486", "i586"):
+        newname = I686
+
+    if not is_valid(newname):
+        raise exception.InvalidArchitectureName(arch=name)
+
+    return newname

nova/exception.py

@@ -1618,3 +1618,7 @@ class ImageVCPUTopologyRangeExceeded(Invalid):
 class ImageVCPULimitsRangeImpossible(Invalid):
     msg_fmt = _("Requested vCPU limits %(sockets)d:%(cores)d:%(threads)d "
                 "are impossible to satisfy for vcpus count %(vcpus)d")
+
+
+class InvalidArchitectureName(Invalid):
+    msg_fmt = _("Architecture name '%(arch)s' is not recognised")

nova/tests/compute/test_arch.py

@@ -0,0 +1,56 @@
+#    Copyright (C) 2014 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import os
+
+import mock
+
+from nova.compute import arch
+from nova import exception
+from nova import test
+
+
+class ArchTest(test.NoDBTestCase):
+
+    @mock.patch.object(os, "uname")
+    def test_host(self, mock_uname):
+        os.uname.return_value = (
+            'Linux',
+            'localhost.localdomain',
+            '3.14.8-200.fc20.x86_64',
+            '#1 SMP Mon Jun 16 21:57:53 UTC 2014',
+            'i686'
+        )
+
+        self.assertEqual(arch.I686, arch.from_host())
+
+    def test_valid_string(self):
+        self.assertTrue(arch.is_valid("x86_64"))
+
+    def test_valid_constant(self):
+        self.assertTrue(arch.is_valid(arch.X86_64))
+
+    def test_valid_bogus(self):
+        self.assertFalse(arch.is_valid("x86_64wibble"))
+
+    def test_canonicalize_i386(self):
+        self.assertEqual(arch.I686, arch.canonicalize("i386"))
+
+    def test_canonicalize_case(self):
+        self.assertEqual(arch.X86_64, arch.canonicalize("X86_64"))
+
+    def test_canonicalize_bogus(self):
+        self.assertRaises(exception.InvalidArchitectureName,
+                          arch.canonicalize,
+                          "x86_64wibble")