[pve-devel] [PATCH pve-docs] qemu: add cpu models documentation

Fri Jun 9 19:25:02 CEST 2023

add doc for differents cpu models including
new x86-64-vX models

Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 qm.adoc | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 138 insertions(+), 7 deletions(-)

diff --git a/qm.adoc b/qm.adoc
index c6dc652..780634f 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -353,6 +353,9 @@ CPU Type
 QEMU can emulate a number different of *CPU types* from 486 to the latest Xeon
 processors. Each new processor generation adds new features, like hardware
 assisted 3d rendering, random number generation, memory protection, etc ...
+Also, a current generation can be upgraded through microcode update with bugs
+or security fixes.
+
 Usually you should select for your VM a processor type which closely matches the
 CPU of the host system, as it means that the host CPU features (also called _CPU
 flags_ ) will be available in your VMs. If you want an exact match, you can set
@@ -360,17 +363,145 @@ the CPU type to *host* in which case the VM will have exactly the same CPU flags
 as your host system.
 
 This has a downside though. If you want to do a live migration of VMs between
-different hosts, your VM might end up on a new system with a different CPU type.
+different hosts, your VM might end up on a new system with a different CPU type
+or a different microcode.
 If the CPU flags passed to the guest are missing, the qemu process will stop. To
-remedy this QEMU has also its own CPU type *kvm64*, that {pve} uses by defaults.
-kvm64 is a Pentium 4 look a like CPU type, which has a reduced CPU flags set,
-but is guaranteed to work everywhere.
+remedy this QEMU has also its own virtual CPU types, that {pve} uses by defaults.
+
+Default is x86-64-v2-AES, compatible with Intel >= Westmere and Amd >= Opteron_G4
+
+In short:
 
-In short, if you care about live migration and moving VMs between nodes, leave
-the kvm64 default. If you don’t care about live migration or have a homogeneous
-cluster where all nodes have the same CPU, set the CPU type to host, as in
+If you don’t care about live migration or have a homogeneous cluster where 
+all nodes have the same CPU and same microcode version, set the CPU type to host, as in
 theory this will give your guests maximum performance.
 
+if you care about live migration and security, and you have only Intel CPU or only AMD CPU,
+choose the lowest generation cpu model of your cluster.
+
+if you care about live migration without security, or have mixed intel/amd cluster,
+choose the lowest compatible virtual qemu type.
+
+NOTE: Intel <> AMD migrations have no guarantee to work
+
+
+Intel CPU Types since 2007
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+https://en.wikipedia.org/wiki/List_of_Intel_Xeon_processors[Intel Processors]
+
+* 'Nahelem' : https://fr.wikipedia.org/wiki/Nehalem[1th generation of the Intel Core Processor]
++
+* 'Nahelem-IBRS (v2)' : add spectre (+spec-ctrl)
++
+* 'Westmere' : https://en.wikipedia.org/wiki/Westmere_(microarchitecture)[1th generation of the Intel Core Processor (Xeon E7-)]
++
+* 'Westmere-IBRS (v2)' : add spectre (+spec-ctrl)
++
+* 'SandyBridge' : https://fr.wikipedia.org/wiki/Sandy_Bridge[2th generation of the Intel Core Processor]
++
+* 'SandyBridge-IBRS (v2)' : add spectre v1 protection (+spec-ctrl)
++
+* 'IvyBridge' : https://en.wikipedia.org/wiki/Ivy_Bridge_(microarchitecture)[3th generation of the Intel Core Processor]
++
+* 'IvyBridge-IBRS (v2)': add spectre v1 protection (+spec-ctrl)
++
+* 'Haswell' : https://fr.wikipedia.org/wiki/Haswell_(microarchitecture)[4th generation of the Intel Core Processor]
++
+* 'Haswell-noTSX (v2)' : disable TSX (-hle,-rtm)
++
+* 'Haswell-IBRS (v3)' : readd TSX, add spectre (+hle,+rtm, +spec-ctrl)
++
+* 'Harwell-noTSX-IBRS (v4)' : disable TSX (-hle,-rtm)
++
+* 'Broadwell': https://en.wikipedia.org/wiki/Broadwell_(microarchitecture)[5th generation of the Intel Core Processor]
++
+* 'Skylake': https://en.wikipedia.org/wiki/Skylake_(microarchitecture)[1st generation Xeon Scalable server processors]
++
+* 'Skylake-IBRS (v2)' : add +spec-ctrl,-clflushopt
++
+* 'Skylake-noTSX-IBRS (v3)' : disable TSX (-hle, -rtm)
++
+* 'Skylake-v4': add EPT switching (+vmx-eptp-switching)
++
+* 'Cascadelake': https://en.wikipedia.org/wiki/Cascade_Lake_(microprocessor)[2nd generation Xeon scalable processor]
++
+* 'Cascadelake-v2' : add arch_capabilities msr (+arch-capabilities,+rdctl-no,+ibrs-all,+skip-l1dfl-vmentry,+mds-no)
++
+* 'Cascadelake-v3' : disable TSX (-hle, -rtm)
++
+* 'Cascadelake-v4' : add EPT switching (+vmx-eptp-switching)
++
+* 'Cascadelake-v5' : add XSAVES (+xsaves,+vmx-xsaves)
++
+* 'CooperLake' : https://en.wikipedia.org/wiki/Cooper_Lake_(microprocessor)[3rd generation Xeon scalable processors for 4 & 8 sockets servers]
++
+* 'CooperLake-v2' : add XSAVES (+xsaves,+vmx-xsaves)
++
+* 'IceLake': https://en.wikipedia.org/wiki/Ice_Lake_(microprocessor)[3rd generation Xeon Scalable server processors]
++
+* 'Icelake-v2' : disable TSX(-hle,-rtm)
++
+* 'Icelake-v3' : add arch_capabilities msr (+arch-capabilities, +rdctl-no, +ibrs-all, +skip-l1dfl-vmentry,+mds-no,+pschange-mc-no,+taa-no)
++
+* 'Icelake-v4' : add missing flags (+sha-ni,+avx512ifma,+rdpid,+fsrm,+vmx-rdseed-exit,+vmx-pml,+vmx-eptp-switching)
++
+* 'Icelake-v5' : add XSAVES (+xsaves,+vmx-xsaves)
++
+* 'Icelake-v6' : add "5-level EPT" (+vmx-page-walk-5)
++
+* 'Sapphire Rapids' : https://en.wikipedia.org/wiki/Sapphire_Rapids[4th generation Xeon Scalable server processors]
+
+AMD CPU Types since 2007
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+https://en.wikipedia.org/wiki/List_of_AMD_processors[AMD Processors]
+
+* 'Opteron_G3' : https://en.wikipedia.org/wiki/AMD_10h[K10]
++
+* 'Opteron_G4' : https://en.wikipedia.org/wiki/Bulldozer_(microarchitecture)[Bulldozer]
++
+* 'Opteron_G5' :  https://en.wikipedia.org/wiki/Piledriver_(microarchitecture)[Piledriver]
++
+* 'EPYC' : https://en.wikipedia.org/wiki/Zen_(first_generation)[1st Generation of Zen Processors]
++
+* 'EPYC-IBPB (v2)' : add spectre v1 protection (+ibpb)
++
+* 'EPYC-v3' : add missing flags (+perfctr-core,+clzero,+xsaveerptr,+xsaves)
++
+* 'EPYC-Rome' : https://en.wikipedia.org/wiki/Zen_2[2nd Generation of Zen Processors]
++
+* 'EPYC-Rome-v2' : add spectre v2,v4 protection (+ibrs,+amd-ssbd)
++
+* 'EPYC-Milan' : https://en.wikipedia.org/wiki/Zen_3[3th Generation of Zen Processors]
++
+* 'EPYC-Milan-v2' : add missing flags (+vaes,+vpclmulqdq,+stibp-always-on,+amd-psfd,+no-nested-data-bp,+lfence-always-serializing,+null-sel-clr-base
+
+Qemu CPU Types
+^^^^^^^^^^^^^^
+
+Qemu also provide virtual cpu types, compatible with both intel/amd.
+
+NOTE: To keep best compatibility, no security flag for spectre/meltdown/... exist in qemu virtual types, so you need to do it manually
+
+Historically, Proxmox had the kvm64 cpu model, with only pentium4 cpu flags enabled, so performance was not great for some workload.
+
+In the summer of 2020, AMD, Intel, Red Hat, and SUSE collaborated to define three x86-64 microarchitecture levels on top of the x86-64 baseline, 
+with modern flags enabled. https://gitlab.com/x86-psABIs/x86-64-ABI[x86-64-ABI specs]
+
+Some newer distro like Centos9 are now built with x86-64-v2 flags as minimum requirement !
+
+
+* 'kvm64 (v1)' : Compatible >=pentium4 , >= phenom
++
+* 'x86-64-v2' : Compatible >= Nehalem, >= Opteron_G4. add cx16,lahf-lm,popcnt,pni,sse4.1,sse4.2,ssse3
++
+* 'x86-64-v2-AES' : Compatible >= Westmere, >= Opteron_G4 : add aes
++
+* 'x86-64-v3' : Compatible >= Broadwell, >= Epyc : add +avx,+avx2,+bmi1,+bmi2,+f16c,+fma,+movbe,xsave
++
+* 'x86-64-v4' : Compatible >= Skylake , >= EPYC-Genoa(V4) : add +avx512f, +avx512bw, +avx512cd,+avx512dq,+avx512vl
+
 Custom CPU Types
 ^^^^^^^^^^^^^^^^
 
-- 
2.30.2



