PVE中CPU类型简析

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