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

[Janosch Frank]

On 12/3/19 6:44 PM, Cornelia Huck wrote:
> On Tue,  3 Dec 2019 08:28:11 -0500
> Janosch Frank <address@hidden> 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 <address@hidden>
>> Reviewed-by: Thomas Huth <address@hidden>
>> Acked-by: David Hildenbrand <address@hidden>
>> ---
>>  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...

I have not written those comments, I merely refuse to delete them :)
We still reset some state in the kernel, I'm not sure how much of that
is already exposed via ioctls to QEMU, so I won't remove the comment.

> 
>> -    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?

See above

> 
>> +     * 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);
>> +    }
>> +}
>

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