I'm using Opteron 6386SE processor, 16 cores. It's capabilites (flags) are here: CPU World

But when I run cat /proc/cpuinfo (dom0 or guest), flags are missing, for example SSE3 and SSE4.

flags : fpu de tsc msr pae mce cx8 apic mca cmov pat clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt1

Generally, the list is very short. When I check my desktop APU or Xeon processor, it contains dozens of features. Is this normal? Are missing flags something to worry about? Our users complain about performance of this machine and I worry that something bad is going on here. htop says all cores are there and working hard, etc.


xen hides many CPU flags from the control domain, dom0 because dom0 itself is a virtual machine. This is a documented behavior.

From Xen doc:

Xen dom0 is actually a virtual machine, so it doesn't see all the cpu flags as Xen hypervisor is hiding some flags from dom0.

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