host capability

目前通过ComputeCapabilitiesFilter 是可以做到cpu 指令集的filter，ComputeCapabilitiesFilter 是通过flavor的extra_spe来传递的。

传递的形式为：capabilities:cpu_info:features=ssse3

实现方式：

1.compute_capabilities_filter.py中首先解析flavor-extra_spec ， 得到capabilities:cpu_info:features

                if scope[0] != "capabilities":
                    continue

2.得到host_state中的cpu_info:features

(Pdb) pp host_state.cpu_info
u'{"vendor": "Intel", "model": "SandyBridge", "arch": "x86_64", "features": 
["pge", "avx", "clflush", "sep", "syscall", "vme", "dtes64", "msr", "fsgsbase", "xsave", "vmx", 
"erms", "xtpr", "cmov", "smep", "ssse3", "est", "pat", "monitor", "smx", "pbe", 
"lm", "tsc", "nx", "fxsr", "tm", "sse4.1", "pae", "sse4.2", "pclmuldq", "acpi", 
"tsc-deadline", "mmx", "osxsave", "cx8", "mce", "de", "tm2", "ht", "pse", "lahf_lm", 
"popcnt", "mca", "apic", "sse", "f16c", "ds", "pni", "rdtscp", "aes", "sse2", "ss", "ds_cpl", 
"pcid", "fpu", "cx16", "pse36", "mtrr", "pdcm", "rdrand", "x2apic"], 
"topology": {"cores": 2, "cells": 1, "threads": 2, "sockets": 1}}'

pp instance_type
Flavor(created_at=None,deleted=False,deleted_at=None,disabled=False,ephemeral_gb=0,
extra_specs={capabilities:cpu_info:arch='x86_64',capabilities:cpu_info:features='<or> acpi,adx,avx,avx2'},
flavorid='',id=2,is_public=True,memory_mb=512,name='m1.tiny',projects=<?>,root_gb=1,rxtx_factor=1.0,swap=0,updated_at=None,vcpu_weight=0,vcpus=1)

(Pdb) pp scope
[u'cpu_info', u'features']

(Pdb) pp req
u'<or> acpi,adx,avx,avx2'

3. 最后比较req中cpu的需要是否host_state中的cpu_info:features能满足。

那么，host_state中的cpu_info:features怎么获得？

1.resource_tracker.py:  self.compute_node.update_from_virt_driver(resources)

    def update_from_virt_driver(self, resources):
        # NOTE(pmurray): the virt driver provides a dict of values that
        # can be copied into the compute node. The names and representation
        # do not exactly match.
        # TODO(pmurray): the resources dict should be formalized.
        keys = ["vcpus", "memory_mb", "local_gb", "cpu_info",
                "vcpus_used", "memory_mb_used", "local_gb_used",
                "numa_topology", "hypervisor_type",
                "hypervisor_version", "hypervisor_hostname",
                "disk_available_least", "host_ip"]
        for key in keys:
            if key in resources:
                self[key] = resources[key]

2.compute_node 把信息report给 scheduler，filter就得到了 scheduler的host_state

Nova中还有一个object VirtCPUModel, 它是 instance object 的一部分，用来描述guest cpu模型，其详细说明在：

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/sect-libvirt-dom-xml-cpu-model-top.html

@base.NovaObjectRegistry.register
class VirtCPUModel(base.NovaObject):
    # Version 1.0: Initial version
    VERSION = '1.0'

    fields = {
        'arch': fields.ArchitectureField(nullable=True),
        'vendor': fields.StringField(nullable=True),
        'topology': fields.ObjectField('VirtCPUTopology',
                                       nullable=True),
        'features': fields.ListOfObjectsField("VirtCPUFeature",
                                              default=[]),
        'mode': fields.CPUModeField(nullable=True),
        'model': fields.StringField(nullable=True),
        'match': fields.CPUMatchField(nullable=True),
    }

object的填充方式：

        guest.cpu = self._get_guest_cpu_config(
            flavor, image_meta, guest_numa_config.numaconfig,
            instance.numa_topology)

        # Notes(yjiang5): we always sync the instance's vcpu model with
        # the corresponding config file.
        instance.vcpu_model = self._cpu_config_to_vcpu_model(
            guest.cpu, instance.vcpu_model)

mode/model通过nova.conf来配置

    def _get_guest_cpu_model_config(self):
        mode = CONF.libvirt.cpu_mode
        model = CONF.libvirt.cpu_model

topology 通过flave-extra_spec/ image meta

virt.hardware.py

def _get_cpu_topology_constraints(flavor, image_meta):
    """Get the topology constraints declared in flavor or image

    :param flavor: Flavor object to read extra specs from
    :param image_meta: nova.objects.ImageMeta object instance

    Gets the topology constraints from the configuration defined
    in the flavor extra specs or the image metadata. In the flavor
    this will look for

     hw:cpu_sockets - preferred socket count
     hw:cpu_cores - preferred core count
     hw:cpu_threads - preferred thread count
     hw:cpu_max_sockets - maximum socket count
     hw:cpu_max_cores - maximum core count
     hw:cpu_max_threads - maximum thread count

    In the image metadata this will look at

     hw_cpu_sockets - preferred socket count
     hw_cpu_cores - preferred core count
     hw_cpu_threads - preferred thread count
     hw_cpu_max_sockets - maximum socket count
     hw_cpu_max_cores - maximum core count
     hw_cpu_max_threads - maximum thread count

feature 也是通过flave-extra_spec/ image meta:

class VirtCPUFeature(base.NovaObject):
    VERSION = '1.0'

    fields = {
        'policy': fields.CPUFeaturePolicyField(nullable=True),
        'name': fields.StringField(nullable=False),
    }

        features = [objects.VirtCPUFeature(
            name=f.name,
            policy=f.policy) for f in cpu_config.features]
        vcpu_model.features = features

virt.hardware.py

def _add_cpu_pinning_constraint(flavor, image_meta, numa_topology):
    flavor_pinning = flavor.get('extra_specs', {}).get("hw:cpu_policy")
    image_pinning = image_meta.properties.get("hw_cpu_policy")

实现了cpu instruction 规则force/require/optional/disable/forbid。

通过image来限定有2种：

ImagePropertiesFilter

根据instance's image上定义的属性来过滤，熟悉包括

architecture, hypervisor type, hypervisor version (for Xen hypervisor type only), and virtual machine mode。

其中，他们的值可以为：

arch:
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,
]

HVType:
ALL = (
    BAREMETAL,
    BHYVE,
    DOCKER,
    FAKE,
    HYPERV,
    IRONIC,
    KQEMU,
    KVM,
    LXC,
    LXD,
    OPENVZ,
    PARALLELS,
    PHYP,
    QEMU,
    TEST,
    UML,
    VBOX,
    VIRTUOZZO,
    VMWARE,
    XEN,
    ZVM,
)

VMMode:
ALL = [HVM, XEN, UML, EXE]

如果image->properties中没有这些属性，则通过过滤；如果有这些属性，而host->capabilities->supportedinstances没有，返回False。

比如，

$ glance image-update img-uuid --property architecture=arm --property hypervisor_type=qemu

2     AggregateImagePropertiesIsolation: 
匹配属性定义在 image的元数据中,用于对这些 aggregate 组进行匹配

比如下面这个 aggregate 分组 myWinAgg 将 windows 系统作为元数据 os=windows

$ nova aggregate-details MyWinAgg
+----+----------+-------------------+------------+---------------+
| Id | Name     | Availability Zone | Hosts      | Metadata      |
+----+----------+-------------------+------------+---------------+
| 1  | MyWinAgg | None              | 'sf-devel' | 'os=windows'  |
+----+----------+-------------------+------------+---------------+

在这个理子中,因为下面 win-2012的镜像中有 windows 的属性, 通过他启动的虚拟机实例会再 sf-devel 分组上启动.

$ glance image-show Win-2012
+------------------+--------------------------------------+
| Property         | Value                                |
+------------------+--------------------------------------+
| Property 'os'    | windows                              |
| checksum         | f8a2eeee2dc65b3d9b6e63678955bd83     |
| container_format | ami                                  |
| created_at       | 2013-11-14T13:24:25                  |

目前社区关于这块的工作：

https://review.openstack.org/#/c/286520/3/specs/newton/approved/expose-host-capabilities.rst

打算扩展和统一host capability，主要在现有的host capability之上扩展以下3个方面：

1. 版本capability
2. 用在image filter的architecture, hypervisor type, VM mode
3. 不易被发现的e.g.: SSD, SR-IOV, fibre channel, etc。

https://review.openstack.org/#/c/309762/2/specs/newton/approved/standardize-capabilities.rst

试图采用枚举的方式(nova.objects.fields.Enum-based)来同一capability的描述模型。

它首先定义了capabilities：

A capability is a *singular* piece of information describing some **functionality** or **feature** of an entity that can be provided to a custom。

比如：

* `hw:x86_cpu_instruction_set_ext:sse`

* `hw:x86_cpu_instruction_set_ext:mmx`

用来表述CPU的指令集

* `virt:libvirt:set_admin_pass`

* `virt:libvirt:huge_pages`

* `virt:libvirt:uefi_boot`

用来表述libvirt的capability.