Enable KVM CPU SSSE3 Support

[sunghost]

Hi,
i tried to enable ssse3 support for my kvm vms: qemu-system-x86_64 -cpu qemu64,+ssse3, but it runs infinity with VNC server running on ::1:5900 .... i canceld it.
My host CPU has ssse3 and newer, i tried kvm64 and qemu64 for kvm vCPU, but its not enabled in kvm.

How can i enable it?
thx

 

[janssensm]

Why don´t you set the cpu type for the vm to host? unless you need live migration off course.
Then all features from your host cpu will be available to this vm.

 

[sunghost]

Yes need live migration.

 

[janssensm]

hmm, I would assume that your flag would work. Did you try to pass it with all the other sse flags your cpu model has?
Or else you could select a cpu model that has this feature and matches your physical cpu types.
Maybe you already reviewed but you can check your possible features with:
qemu-system-x86_64 -cpu help

 

[leesteken]

Usually adding args: -cpu qemu64,+ssse3 to the VM configuration file in the directory /etc/pve/qemu-server/ should do the trick.
Note that the software inside the VM might expect other extensions/flags (like sse2 or sse3) when ssse3 is present and you might need to add more.

PS: You might want to consider use kvm64 instead of qemu64 or better yet: the lowest common CPU type (when they are all Intel or all AMD) and maybe Meltdown/Spectre-flags too.