Re: [PATCH v2 08/13] s390x: protvirt: Add new VCPU reset functions

[Thomas Huth <thuth@redhat.com>]

On 29/11/2019 10.48, Janosch Frank wrote:
> CPU resets for protected guests need to be done via Ultravisor
> calls. Hence we need a way to issue these calls for each reset.
> 
> As we formerly had only one reset function and it was called for
> initial, as well as for the clear reset, we now need a new interface.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
[...]
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index b802d02ff5..5b1ed3acb4 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -154,6 +154,7 @@ static int cap_ri;
>  static int cap_gs;
>  static int cap_hpage_1m;
>  static int cap_protvirt;
> +static int cap_vcpu_resets;
>  
>  static int active_cmma;
>  
> @@ -346,6 +347,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
>      cap_s390_irq = kvm_check_extension(s, KVM_CAP_S390_INJECT_IRQ);
>      cap_protvirt = kvm_check_extension(s, KVM_CAP_S390_PROTECTED);
> +    cap_vcpu_resets = kvm_check_extension(s, KVM_CAP_S390_VCPU_RESETS);
>  
>      if (!kvm_check_extension(s, KVM_CAP_S390_GMAP)
>          || !kvm_check_extension(s, KVM_CAP_S390_COW)) {
> @@ -407,20 +409,44 @@ 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) */
> +    /*
> +     * 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 (cap_vcpu_resets) {
> +        if (kvm_vcpu_ioctl(cs, KVM_S390_VCPU_RESET, type)) {
> +            error_report("CPU reset type %ld failed on CPU %i",
> +                         type, cs->cpu_index);
> +        }
> +        return;
> +    }
>      if (kvm_vcpu_ioctl(cs, KVM_S390_INITIAL_RESET, NULL)) {
>          error_report("Initial CPU reset failed on CPU %i", cs->cpu_index);
>      }

Don't you want to check for type != KVM_S390_VCPU_RESET_NORMAL before
doing the INITIAL_RESET here?

>  }
>  
> +void kvm_s390_reset_vcpu_initial(S390CPU *cpu)
> +{
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_VCPU_RESET_INITIAL);
> +}
> +
> +void kvm_s390_reset_vcpu_clear(S390CPU *cpu)
> +{
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_VCPU_RESET_CLEAR);
> +}
> +
> +void kvm_s390_reset_vcpu_normal(S390CPU *cpu)
> +{
> +    kvm_s390_reset_vcpu(cpu, KVM_S390_VCPU_RESET_NORMAL);
> +}

... otherwise this might reset more things than expected?

Or do I miss something here?

 Thomas