CPU Changes in proxmox 4.0?

[notfixingit]

Setting a KVM VM CPU to type Broadwell on C2750 worked in 3.4 but not in 4.0, also having this same issue with other systems where the type was set to match the host CPU.

Error when trying to start
warning: host doesn't support requested feature: CPUID.01H:ECX.fma [bit 12]
warning: host doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
warning: host doesn't support requested feature: CPUID.01H:ECX.xsave [bit 26]
warning: host doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
warning: host doesn't support requested feature: CPUID.01H:ECX.f16c [bit 29]
warning: host doesn't support requested feature: CPUID.07H:EBX.fsgsbase [bit 0]
warning: host doesn't support requested feature: CPUID.07H:EBX.bmi1 [bit 3]
warning: host doesn't support requested feature: CPUID.07H:EBX.hle [bit 4]
warning: host doesn't support requested feature: CPUID.07H:EBX.avx2 [bit 5]
warning: host doesn't support requested feature: CPUID.07H:EBX.bmi2 [bit 8]
warning: host doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10]
warning: host doesn't support requested feature: CPUID.07H:EBX.rtm [bit 11]
warning: host doesn't support requested feature: CPUID.07H:EBX.rdseed [bit 18]
warning: host doesn't support requested feature: CPUID.07H:EBX.adx [bit 19]
warning: host doesn't support requested feature: CPUID.07H:EBX.smap [bit 20]
warning: host doesn't support requested feature: CPUID.0DH:EAX.xsaveopt [bit 0]
kvm: Host doesn't support requested features


Changing Type to "host" allows the VM's to boot. Did something change in 4.0 or am I missing something here?


Thanks in advance.

 

[dietmar]

Changing Type to "host" allows the VM's to boot. Did something change in 4.0 or am I missing something here?

yes - there is a check to verify that requested CPU features really exists.

 

[notfixingit]

Gotcha, but the CPU in this particular case is a Broadwell (Atom C2750), so is the check looking for all possible features of Broadwell and some of the same type cpu's just do not have all those features? Just confused as the host CPU is a Broadwell

On another system having the same issue with Xeon E3-1245 v3 (Hasewell) when set to Hasewell.


Thanks again Dietmar!

 

[MoxProxxer]

I have to necromance this for Proxmox 7.0.

VM CPU set to Haswell will not boot

kvm: warning: host doesn't support requested feature: CPUID.07H:EBX.hle [bit 4]
kvm: warning: host doesn't support requested feature: CPUID.07H:EBX.rtm [bit 11]

The system is ofc a Haswell
model name : Intel(R) Xeon(R) CPU E5-2630L v3 @ 1.80GHz

setting VM CPU to "host" works.

 

[leesteken]

The system is ofc a Haswell
model name : Intel(R) Xeon(R) CPU E5-2630L v3 @ 1.80GHz

EDIT: Sorry, I did not check the v3. It is indeed advertised as Haswell, but it appears not to support all features required by KVM for Haswell. This is not something that can be fixed or worked-around by Proxmox if the hardware reports that it does not support all Haswell features. Maybe report this to QEMU?

 

[MoxProxxer]

EDIT: Sorry, I did not check the v3. It is indeed advertised as Haswell, but it appears not to support all features required by KVM for Haswell. This is not something that can be fixed or worked-around by Proxmox if the hardware reports that it does not support all Haswell features. Maybe report this to QEMU?

The Xeon v3 is the representative for the Haswell architecture. What I can imagine happens here, is that some features might be turned off by the BIOS (just a hypothesis), so it looks like a Haswell minus X to QEMU. I can look into it once I fix my other more pressing config problems.

 

[leesteken]

It is sold during the Haswell era but designed at an earlier time (Sandy Bridge with some additions and improvements). It just does not support the same features (in hardware) that processors designed for/during the Haswell era support.
EDIT: This turns out to be completely wrong.

 

[MoxProxxer]

It is sold during the Haswell era but designed at an earlier time (Sandy Bridge with some additions and improvements). It just does not support the same features (in hardware) that processors designed for/during the Haswell era support.

This is simply not true. https://en.wikipedia.org/wiki/Haswell_(microarchitecture)

For starters, Haswell is a true successor (tock) to Ivy Bridge which is a successor (tick) to Sandy Bridge. Second, while there is not "the one single Haswell" (because it's merely an Intel code name), this particular Xeon v3 is a "Haswell-EP" and it was actually released a year after the first Haswells (for Desktop, Mobile) were released.

If anything - and you're probably right this could be in the responsibility of Qemu - if anyone wants to talk about "Haswell" and its features, he/she should define that featureset as the smallest common denominator and not a full feature set.

Be it as it may, the "host" CPU setting is a good enough workaround for now, but the behavior can still be considered a bug, becuase if a Haswell-EP is not a Haswell, nothing is.

edit:

Aaaand solved.

TSX was another feature brought over from the non-K-series SKUs, until August 2014 when a microcode update disabled TSX due to a bug that was discovered in its implementation

=> Haswell-NoTSX is an option, and works.

 

[leesteken]

Nice! And thank you for correcting me and taking the trouble to report back on this for others.