[Bug 1914748] [NEW] Confuse error message when KVM can not start requested CPU

[Philippe Mathieu-Daudé]

Public bug reported:

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.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: arm ui

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https://bugs.launchpad.net/bugs/1914748

Title:
  Confuse error message when KVM can not start requested CPU

Status in QEMU:
  New

Bug description:
  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.

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