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

["Richard W.M. Jones" <rjones@redhat.com>]

On Tue, Dec 09, 2014 at 11:50:31AM +0100, Kashyap Chamarthy 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;
>     
>     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 ..."

Kashyap,

Can you try modifying src/launch-direct.c to see if we can pass

  -cpu cortex-a7

and if that fixes the problem?

If that does solve the problem, the question becomes how to detect the
right CPU (either cortex-a7, cortex-a15, cortex-a57, ...)  This
information isn't easily available to libguestfs AFAIK.

I really think that qemu should just "do the right thing" though.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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