Confuse error message when KVM can not start requested CPU

[Philippe Mathieu-Daudé]

As of commit 1ba089f2255, on Cavium CN8890 (ThunderX cores):

$ qemu-system-aarch64 -display none -accel kvm -M virt,gic-version=3 -accel kvm -cpu cortex-a57 --trace \*kvm_vcpu\*
kvm_vcpu_ioctl cpu_index 0, type 0x4020aeae, arg 0xffff9b7f9b18
qemu-system-aarch64: kvm_init_vcpu: kvm_arch_init_vcpu failed (0): Invalid argument

(same using "-cpu cortex-a53" or cortex-a72).

Explanation from Peter Maydell on IRC:
> using a specific cpu type will only work with KVM if the host CPU really is that
> exact CPU type, otherwise, use "-cpu host" or "-cpu max"

Having a better error description would help to understand the reason.

[Philippe Mathieu-Daudé (philmd)]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'invalid' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/239