Re: [PATCH v2 2/3] s390x: Add missing vcpu reset functions

[Thomas Huth <thuth@redhat.com>]

On 02/12/2019 15.01, Janosch Frank wrote:
> Up to now we only had an ioctl to reset vcpu data QEMU couldn't reach
> for the initial reset, which was also called for the clear reset. To
> be architecture compliant, we also need to clear local interrupts on a
> normal reset.
> 
> Because of this and the upcoming protvirt support we need to add
> ioctls for the missing clear and normal resets.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
[...]
> @@ -403,20 +405,44 @@ int kvm_arch_destroy_vcpu(CPUState *cs)
>      return 0;
>  }
>  
> -void kvm_s390_reset_vcpu(S390CPU *cpu)
> +static void kvm_s390_reset_vcpu(S390CPU *cpu, unsigned long type)
>  {
>      CPUState *cs = CPU(cpu);
>  
> -    /* The initial reset call is needed here to reset in-kernel
> -     * vcpu data that we can't access directly from QEMU
> -     * (i.e. with older kernels which don't support sync_regs/ONE_REG).
> -     * Before this ioctl cpu_synchronize_state() is called in common kvm
> -     * code (kvm-all) */
> -    if (kvm_vcpu_ioctl(cs, KVM_S390_INITIAL_RESET, NULL)) {
> -        error_report("Initial CPU reset failed on CPU %i", cs->cpu_index);
> +    /*
> +     * The reset call is needed here to reset in-kernel vcpu data that
> +     * we can't access directly from QEMU (i.e. with older kernels
> +     * which don't support sync_regs/ONE_REG).  Before this ioctl
> +     * cpu_synchronize_state() is called in common kvm code
> +     * (kvm-all).
> +     */
> +    if (kvm_vcpu_ioctl(cs, type)) {
> +        error_report("CPU reset failed on CPU %i", cs->cpu_index);

In case you respin, maybe also print the "type" variable here?

>      }
>  }
>  
> +void kvm_s390_reset_vcpu_initial(S390CPU *cpu)
> +{
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_INITIAL_RESET);
> +}
> +
> +void kvm_s390_reset_vcpu_clear(S390CPU *cpu)
> +{
> +    if (!cap_vcpu_resets) {
> +        kvm_s390_reset_vcpu(cpu, KVM_S390_INITIAL_RESET);
> +    } else {
> +        kvm_s390_reset_vcpu(cpu, KVM_S390_CLEAR_RESET);
> +    }

Cosmetic nit: It's a tiny bit nicer the other way round:

    if (cap_vcpu_resets) {
        kvm_s390_reset_vcpu(cpu, KVM_S390_CLEAR_RESET);
    } else {
        kvm_s390_reset_vcpu(cpu, KVM_S390_INITIAL_RESET);
    }

Anyway,
Reviewed-by: Thomas Huth <thuth@redhat.com>