Re: [Qemu-devel] Cubietruck: cannot create KVM guests: "kvm_init_vcpu failed: Invalid argument"

[Peter Maydell]

On 9 December 2014 at 10:50, Kashyap Chamarthy <address@hidden> wrote:
> Booting a minimal KVM guest throws the below error on Cubietruck:
>
>   "kvm_init_vcpu failed: Invalid argument"
>
> More context and an easy reproducer in this QEMU bug[1] for Fedora.
>
> Context quoting Rich Jones from comment #2:
>
>     "For some reason I thought this had been fixed upstream, but
>     now that I've finally got my CT working again, I see that I
>     am still carrying that patch in my custom qemu.
>
>     diff --git a/target-arm/cpu.c b/target-arm/cpu.c
>     index 5ce7350..04d69d1 100644
>     --- a/target-arm/cpu.c
>     +++ b/target-arm/cpu.c
>     @@ -858,7 +858,7 @@ static void cortex_a15_initfn(Object *obj)
>          set_feature(&cpu->env, ARM_FEATURE_DUMMY_C15_REGS);
>          set_feature(&cpu->env, ARM_FEATURE_CBAR_RO);
>          set_feature(&cpu->env, ARM_FEATURE_LPAE);
>     -    cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A15;
>     +    cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A7;
>          cpu->midr = 0x412fc0f1;
>          cpu->reset_fpsid = 0x410430f0;
>          cpu->mvfr0 = 0x10110222;

This is obviously a bogus patch -- this is the initfn
for Cortex-A15 so telling it to be a Cortex-A7 is wrong
(and would break working setups on A15 hosts).

>     So that's the answer really, it's a qemu bug.  Actually it looks as
>     if qemu contains some code to try to get the host CPU type, but it
>     doesn't work, or maybe we need to pass a -cpu option ..."

Yes, you need to pass a -cpu option. For KVM on ARM, you
always need to either:
 * pass a -cpu option matching the host CPU
 * pass "-cpu host"

The CubieTruck is a Cortex-A7, which we don't have specific
support for in QEMU, so you will need "-cpu host".

thanks
-- PMM