usermode emulation warns about features that are system-only (x2apic, tsc-deadline, pcid, invpcid)
Following #1512 (closed) and with help to @bonzini
$ qemu-i386 -cpu Haswell-noTSX,enforce /bin/ls
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.fma [bit 12]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.tsc-deadline [bit 24]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.01H:ECX.f16c [bit 29]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.07H:EBX.avx2 [bit 5]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.80000001H:EDX.syscall [bit 11]
qemu-i386: warning: TCG doesn't support requested feature: CPUID.80000001H:EDX.lm [bit 29]
qemu-i386: TCG doesn't support requested features