新手在选择CPU类型的时候总会迷糊，这么多cpu类型应该选择哪样？

一：只有基本功能的kvm64

pve默认使用一种叫KVM64类似奔腾4的CPU模型。这个模型只有基础功能。

如下图

从图上可以看到kvm64缺少了很多指令集。

因此kvm64实际上是一个缺少了指令集的玩意儿，如果需要特定的指令集，需要在虚拟配置文件中，加上指令集，例如aes。使cpu性能增强。

我这里给KVM64加上一个aes指令集。

进入系统之后，查看已经有了aes指令集

可以看到KVM64缺少指令集，这让其在某些领域，性能稍差，例如缺少avx指令集。此时就需要在虚拟机配置文件中，为其增加指令集。

二：为什么需要kvm64

kvm64是一个缺少指令集的模型，如果vm需要指令集还需要单独添加指令集，这就变得麻烦。但是KVM64让集群更加的高可用。

在HA热迁移或者容灾恢复时。KVM64给了CPU一个统一的代号，也就是kvm64，这避免了不同处理器之间的兼容问题。

例如，在设置了HA的一个VM上，用的是E5-2630处理器。主机突然不工作，虚拟机自动转到另外一台主机上运行，而此时主机的CPU却是E5-2650 V3。这就会产生一个兼容性问题。明明系统的CPU是e5-2630。一瞬间就变成了e5-2650 v3，操作系统都反应不过来。有兴趣的朋友可以试试，这会发生什么问题。

三：host和架构类型CPU

host也就相当于CPU的完全模拟，即主机是什么CPU，那么虚拟机也是什么CPU。如下图。

相对于host类型，还有一种其他类型，即cpu架构类型，例如haswell/sandybridge。这是cpu的架构。其中haswell是intel第四代cpu架构。

此类架构CPU模型，就是模拟那个架构的CPU，包含了那一代处理器的所有指令集。例如下图模拟的是sandybridge。

注意，一定要遵循向下兼容，向上不兼容的原则。也就是说如果你的CPU是2代的，就不能模拟3代的，除非CPU指令集一样，总不能在软件层面上，多一个指令集呗，这就是无中生有。所以会报错，如下

此类型的CPU，比KVM64性能更强一些，对比host，在ha中，兼容性更强！

2021.10.21更新

CPU type可以使用命令qemu-system-x86_64 -cpu help 去查看，不出意外会有如下输出

CPU类型

• 架构 名称 说明 x86 486 (alias configured by machine type)
• x86 486-v1
• x86 Broadwell (alias configured by machine type)
• x86 Broadwell-IBRS (alias of Broadwell-v3)
• x86 Broadwell-noTSX (alias of Broadwell-v2)
• x86 Broadwell-noTSX-IBRS (alias of Broadwell-v4)
• x86 Broadwell-v1 Intel Core Processor (Broadwell)
• x86 Broadwell-v2 Intel Core Processor (Broadwell, no TSX)
• x86 Broadwell-v3 Intel Core Processor (Broadwell, IBRS)
• x86 Broadwell-v4 Intel Core Processor (Broadwell, no TSX, IBRS)
• x86 Cascadelake-Server (alias configured by machine type)
• x86 Cascadelake-Server-noTSX (alias of Cascadelake-Server-v3)
• x86 Cascadelake-Server-v1 Intel Xeon Processor (Cascadelake)
• x86 Cascadelake-Server-v2 Intel Xeon Processor (Cascadelake) [ARCH_CAPABILITIES]
• x86 Cascadelake-Server-v3 Intel Xeon Processor (Cascadelake) [ARCH_CAPABILITIES, no TSX]
• x86 Cascadelake-Server-v4 Intel Xeon Processor (Cascadelake) [ARCH_CAPABILITIES, no TSX]
• x86 Conroe (alias configured by machine type)
• x86 Conroe-v1 Intel Celeron_4x0 (Conroe/Merom Class Core 2)
• x86 Cooperlake (alias configured by machine type)
• x86 Cooperlake-v1 Intel Xeon Processor (Cooperlake)
• x86 Denverton (alias configured by machine type)
• x86 Denverton-v1 Intel Atom Processor (Denverton)
• x86 Denverton-v2 Intel Atom Processor (Denverton) [no MPX, no MONITOR]
• x86 Dhyana (alias configured by machine type)
• x86 Dhyana-v1 Hygon Dhyana Processor
• x86 EPYC (alias configured by machine type)
• x86 EPYC-IBPB (alias of EPYC-v2)
• x86 EPYC-Milan (alias configured by machine type)
• x86 EPYC-Milan-v1 AMD EPYC-Milan Processor
• x86 EPYC-Rome (alias configured by machine type)
• x86 EPYC-Rome-v1 AMD EPYC-Rome Processor
• x86 EPYC-Rome-v2 AMD EPYC-Rome Processor
• x86 EPYC-v1 AMD EPYC Processor
• x86 EPYC-v2 AMD EPYC Processor (with IBPB)
• x86 EPYC-v3 AMD EPYC Processor
• x86 Haswell (alias configured by machine type)
• x86 Haswell-IBRS (alias of Haswell-v3)
• x86 Haswell-noTSX (alias of Haswell-v2)
• x86 Haswell-noTSX-IBRS (alias of Haswell-v4)
• x86 Haswell-v1 Intel Core Processor (Haswell)
• x86 Haswell-v2 Intel Core Processor (Haswell, no TSX)
• x86 Haswell-v3 Intel Core Processor (Haswell, IBRS)
• x86 Haswell-v4 Intel Core Processor (Haswell, no TSX, IBRS)
• x86 Icelake-Client (alias configured by machine type)
• x86 Icelake-Client-noTSX (alias of Icelake-Client-v2)
• x86 Icelake-Client-v1 Intel Core Processor (Icelake) [deprecated]
• x86 Icelake-Client-v2 Intel Core Processor (Icelake) [no TSX, deprecated]
• x86 Icelake-Server (alias configured by machine type)
• x86 Icelake-Server-noTSX (alias of Icelake-Server-v2)
• x86 Icelake-Server-v1 Intel Xeon Processor (Icelake)
• x86 Icelake-Server-v2 Intel Xeon Processor (Icelake) [no TSX]
• x86 Icelake-Server-v3 Intel Xeon Processor (Icelake)
• x86 Icelake-Server-v4 Intel Xeon Processor (Icelake)
• x86 IvyBridge (alias configured by machine type)
• x86 IvyBridge-IBRS (alias of IvyBridge-v2)
• x86 IvyBridge-v1 Intel Xeon E3-12xx v2 (Ivy Bridge)
• x86 IvyBridge-v2 Intel Xeon E3-12xx v2 (Ivy Bridge, IBRS)
• x86 KnightsMill (alias configured by machine type)
• x86 KnightsMill-v1 Intel Xeon Phi Processor (Knights Mill)
• x86 Nehalem (alias configured by machine type)
• x86 Nehalem-IBRS (alias of Nehalem-v2)
• x86 Nehalem-v1 Intel Core i7 9xx (Nehalem Class Core i7)
• x86 Nehalem-v2 Intel Core i7 9xx (Nehalem Core i7, IBRS update)
• x86 Opteron_G1 (alias configured by machine type)
• x86 Opteron_G1-v1 AMD Opteron 240 (Gen 1 Class Opteron)
• x86 Opteron_G2 (alias configured by machine type)
• x86 Opteron_G2-v1 AMD Opteron 22xx (Gen 2 Class Opteron)
• x86 Opteron_G3 (alias configured by machine type)
• x86 Opteron_G3-v1 AMD Opteron 23xx (Gen 3 Class Opteron)
• x86 Opteron_G4 (alias configured by machine type)
• x86 Opteron_G4-v1 AMD Opteron 62xx class CPU
• x86 Opteron_G5 (alias configured by machine type)
• x86 Opteron_G5-v1 AMD Opteron 63xx class CPU
• x86 Penryn (alias configured by machine type)
• x86 Penryn-v1 Intel Core 2 Duo P9xxx (Penryn Class Core 2)
• x86 SandyBridge (alias configured by machine type)
• x86 SandyBridge-IBRS (alias of SandyBridge-v2)
• x86 SandyBridge-v1 Intel Xeon E312xx (Sandy Bridge)
• x86 SandyBridge-v2 Intel Xeon E312xx (Sandy Bridge, IBRS update)
• x86 Skylake-Client (alias configured by machine type)
• x86 Skylake-Client-IBRS (alias of Skylake-Client-v2)
• x86 Skylake-Client-noTSX-IBRS (alias of Skylake-Client-v3)
• x86 Skylake-Client-v1 Intel Core Processor (Skylake)
• x86 Skylake-Client-v2 Intel Core Processor (Skylake, IBRS)
• x86 Skylake-Client-v3 Intel Core Processor (Skylake, IBRS, no TSX)
• x86 Skylake-Server (alias configured by machine type)
• x86 Skylake-Server-IBRS (alias of Skylake-Server-v2)
• x86 Skylake-Server-noTSX-IBRS (alias of Skylake-Server-v3)
• x86 Skylake-Server-v1 Intel Xeon Processor (Skylake)
• x86 Skylake-Server-v2 Intel Xeon Processor (Skylake, IBRS)
• x86 Skylake-Server-v3 Intel Xeon Processor (Skylake, IBRS, no TSX)
• x86 Skylake-Server-v4 Intel Xeon Processor (Skylake, IBRS, no TSX)
• x86 Snowridge (alias configured by machine type)
• x86 Snowridge-v1 Intel Atom Processor (SnowRidge)
• x86 Snowridge-v2 Intel Atom Processor (Snowridge, no MPX)
• x86 Westmere (alias configured by machine type)
• x86 Westmere-IBRS (alias of Westmere-v2)
• x86 Westmere-v1 Westmere E56xx/L56xx/X56xx (Nehalem-C)
• x86 Westmere-v2 Westmere E56xx/L56xx/X56xx (IBRS update)
• x86 athlon (alias configured by machine type)
• x86 athlon-v1 QEMU Virtual CPU version 2.5+
• x86 core2duo (alias configured by machine type)
• x86 core2duo-v1 Intel(R) Core(TM)2 Duo CPU T7700 @ 2.40GHz
• x86 coreduo (alias configured by machine type)
• x86 coreduo-v1 Genuine Intel(R) CPU T2600 @ 2.16GHz
• x86 kvm32 (alias configured by machine type)
• x86 kvm32-v1 Common 32-bit KVM processor
• x86 kvm64 (alias configured by machine type)
• x86 kvm64-v1 Common KVM processor
• x86 n270 (alias configured by machine type)
• x86 n270-v1 Intel(R) Atom(TM) CPU N270 @ 1.60GHz
• x86 pentium (alias configured by machine type)
• x86 pentium-v1
• x86 pentium2 (alias configured by machine type)
• x86 pentium2-v1
• x86 pentium3 (alias configured by machine type)
• x86 pentium3-v1
• x86 phenom (alias configured by machine type)
• x86 phenom-v1 AMD Phenom(tm) 9550 Quad-Core Processor
• x86 qemu32 (alias configured by machine type)
• x86 qemu32-v1 QEMU Virtual CPU version 2.5+
• x86 qemu64 (alias configured by machine type)
• x86 qemu64-v1 QEMU Virtual CPU version 2.5+
• x86 base base CPU model type with no features enabled
• x86 host KVM processor with all supported host features
• x86 max Enables all features supported by the accelerator in the current host

支持的指令集如下

• 3dnow 3dnowext 3dnowprefetch abm ace2 ace2-en acpi adx aes amd-no-ssb
• amd-ssbd amd-stibp apic arat arch-capabilities avic avx avx2
• avx512-4fmaps avx512-4vnniw avx512-bf16 avx512-fp16 avx512-vp2intersect
• avx512-vpopcntdq avx512bitalg avx512bw avx512cd avx512dq avx512er avx512f
• avx512ifma avx512pf avx512vbmi avx512vbmi2 avx512vl avx512vnni bmi1 bmi2
• bus-lock-detect cid cldemote clflush clflushopt clwb clzero cmov
• cmp-legacy core-capability cr8legacy cx16 cx8 dca de decodeassists ds
• ds-cpl dtes64 erms est extapic f16c flushbyasid fma fma4 fpu fsgsbase
• fsrm full-width-write fxsr fxsr-opt gfni hle ht hypervisor ia64 ibpb ibrs
• ibrs-all ibs intel-pt intel-pt-lip invpcid invtsc kvm-asyncpf
• kvm-asyncpf-int kvm-hint-dedicated kvm-mmu kvm-msi-ext-dest-id
• kvm-nopiodelay kvm-poll-control kvm-pv-eoi kvm-pv-ipi kvm-pv-sched-yield
• kvm-pv-tlb-flush kvm-pv-unhalt kvm-steal-time kvmclock kvmclock
• kvmclock-stable-bit la57 lahf-lm lbrv lm lwp mca mce md-clear mds-no
• misalignsse mmx mmxext monitor movbe movdir64b movdiri mpx msr mtrr
• nodeid-msr npt nrip-save nx osvw pae pat pause-filter pbe pcid pclmulqdq
• pcommit pdcm pdpe1gb perfctr-core perfctr-nb pfthreshold pge phe phe-en
• pks pku pmm pmm-en pn pni popcnt pschange-mc-no pse pse36 rdctl-no rdpid
• rdrand rdseed rdtscp rsba rtm sep serialize sha-ni skinit
• skip-l1dfl-vmentry smap smep smx spec-ctrl split-lock-detect ss ssb-no
• ssbd sse sse2 sse4.1 sse4.2 sse4a ssse3 stibp svm svm-lock svme-addr-chk
• syscall taa-no tbm tce tm tm2 topoext tsc tsc-adjust tsc-deadline
• tsc-scale tsx-ctrl tsx-ldtrk umip v-vmsave-vmload vaes vgif virt-ssbd
• vmcb-clean vme vmx vmx-activity-hlt vmx-activity-shutdown
• vmx-activity-wait-sipi vmx-apicv-register vmx-apicv-vid vmx-apicv-x2apic
• vmx-apicv-xapic vmx-cr3-load-noexit vmx-cr3-store-noexit
• vmx-cr8-load-exit vmx-cr8-store-exit vmx-desc-exit vmx-encls-exit
• vmx-entry-ia32e-mode vmx-entry-load-bndcfgs vmx-entry-load-efer
• vmx-entry-load-pat vmx-entry-load-perf-global-ctrl vmx-entry-load-pkrs
• vmx-entry-load-rtit-ctl vmx-entry-noload-debugctl vmx-ept vmx-ept-1gb
• vmx-ept-2mb vmx-ept-advanced-exitinfo vmx-ept-execonly vmx-eptad
• vmx-eptp-switching vmx-exit-ack-intr vmx-exit-clear-bndcfgs
• vmx-exit-clear-rtit-ctl vmx-exit-load-efer vmx-exit-load-pat
• vmx-exit-load-perf-global-ctrl vmx-exit-load-pkrs
• vmx-exit-nosave-debugctl vmx-exit-save-efer vmx-exit-save-pat
• vmx-exit-save-preemption-timer vmx-flexpriority vmx-hlt-exit vmx-ins-outs
• vmx-intr-exit vmx-invept vmx-invept-all-context vmx-invept-single-context
• vmx-invept-single-context vmx-invept-single-context-noglobals
• vmx-invlpg-exit vmx-invpcid-exit vmx-invvpid vmx-invvpid-all-context
• vmx-invvpid-single-addr vmx-io-bitmap vmx-io-exit vmx-monitor-exit
• vmx-movdr-exit vmx-msr-bitmap vmx-mtf vmx-mwait-exit vmx-nmi-exit
• vmx-page-walk-4 vmx-page-walk-5 vmx-pause-exit vmx-ple vmx-pml
• vmx-posted-intr vmx-preemption-timer vmx-rdpmc-exit vmx-rdrand-exit
• vmx-rdseed-exit vmx-rdtsc-exit vmx-rdtscp-exit vmx-secondary-ctls
• vmx-shadow-vmcs vmx-store-lma vmx-true-ctls vmx-tsc-offset
• vmx-unrestricted-guest vmx-vintr-pending vmx-vmfunc
• vmx-vmwrite-vmexit-fields vmx-vnmi vmx-vnmi-pending vmx-vpid
• vmx-wbinvd-exit vmx-xsaves vmx-zero-len-inject vpclmulqdq waitpkg
• wbnoinvd wdt x2apic xcrypt xcrypt-en xgetbv1 xop xsave xsavec xsaveerptr

 可以看到在CPU type中有一个叫作x86 max


看说明，是Enables all features supported by the accelerator in the current host理论上来说，此项就是KVM中性能最好的CPU模型

在pve面板上如下