Re: qemu-kvm requires apic initialized before vcpu main loop

[Jan Kiszka <jan.kiszka@siemens.com>]

Marcelo Tosatti wrote:
> Otherwise a zero apic base is loaded into KVM, which results
> in interrupts being lost until a proper apic base with enabled 
> bit set is loaded.
> 
> Fixes WinXP migration in qemu-kvm origin/next.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/hw/apic.c b/hw/apic.c
> index 627ff98..45a4d2b 100644
> --- a/hw/apic.c
> +++ b/hw/apic.c
> @@ -1131,6 +1131,11 @@ int apic_init(CPUState *env)
>      vmstate_register(s->idx, &vmstate_apic, s);
>      qemu_register_reset(apic_reset, s);
>  
> +    /* apic_reset must be called before the vcpu threads are initialized and load 
> +     * registers, in qemu-kvm.
> +     */
> +    apic_reset(s);
> +
>      local_apics[s->idx] = s;
>      return 0;
>  }

Heals the issue I saw with Win2003 Server as well.

Looks all a bit messy though. Hope we can establish a more regular and
less fragile model on the midterm. I wonder if it wouldn't be better to
do write-back of the local APIC state along with the register state on
vmrun (and only there!). The same would apply to things like mpstate,
TSC MSR, or the guest debugging state. The reset/vmloading/hw-emulation
code would only declare what kind of write-back it wishes: register
state only, partial (excluding everything that touches continuously
running timers), full. Well, basically the model I suggested for proper
mpstate write-back, just even more generalized.

Jan

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