Re: [PATCH v3 2/4] s390x: Add missing vcpu reset functions

[Cornelia Huck <cohuck@redhat.com>]

On Tue,  3 Dec 2019 08:28:11 -0500
Janosch Frank <frankja@linux.ibm.com> wrote:

> Up to now we only had an ioctl to reset vcpu data QEMU couldn't reach
> for the initial reset, and that 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>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/cpu.c       | 16 +++++++++++++--
>  target/s390x/kvm-stub.c  | 10 +++++++++-
>  target/s390x/kvm.c       | 42 ++++++++++++++++++++++++++++++++--------
>  target/s390x/kvm_s390x.h |  4 +++-
>  4 files changed, 60 insertions(+), 12 deletions(-)
> 
> diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> index 829ce6ad54..4973365d6c 100644
> --- a/target/s390x/cpu.c
> +++ b/target/s390x/cpu.c
> @@ -139,8 +139,20 @@ static void s390_cpu_reset(CPUState *s, cpu_reset_type type)
>      }
>  
>      /* Reset state inside the kernel that we cannot access yet from QEMU. */

For the last iteration, I asked about the 'yet' here...

> -    if (kvm_enabled() && type != S390_CPU_RESET_NORMAL) {
> -        kvm_s390_reset_vcpu(cpu);
> +    if (kvm_enabled()) {
> +        switch (type) {
> +        case S390_CPU_RESET_CLEAR:
> +            kvm_s390_reset_vcpu_clear(cpu);
> +            break;
> +        case S390_CPU_RESET_INITIAL:
> +            kvm_s390_reset_vcpu_initial(cpu);
> +            break;
> +        case S390_CPU_RESET_NORMAL:
> +            kvm_s390_reset_vcpu_normal(cpu);
> +            break;
> +        default:
> +            g_assert_not_reached();
> +        }
>      }
>  }
>  

(...)

> @@ -403,17 +405,41 @@ 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

...and this reference to 'older kernels' here.

Are the comments still correct/relevant?

> +     * 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 type %lx",
> +                     cs->cpu_index, type);
> +    }
> +}