linux-kernel - Re: [PATCH v10 2/3] KVM: s390: guest support for topology function

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Date:   Tue, 28 Jun 2022 16:38:23 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Nico Boehr <nrb@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, cohuck@...hat.com,
        david@...hat.com, thuth@...hat.com, imbrenda@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com, wintera@...ux.ibm.com,
        seiden@...ux.ibm.com
Subject: Re: [PATCH v10 2/3] KVM: s390: guest support for topology function



On 6/24/22 08:56, Nico Boehr wrote:
> Quoting Pierre Morel (2022-06-20 14:54:36)
> [...]
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index 766028d54a3e..bb54196d4ed6 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
> [...]
>> @@ -3403,6 +3426,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>>          rc = kvm_s390_vcpu_setup(vcpu);
>>          if (rc)
>>                  goto out_ucontrol_uninit;
>> +
>> +       kvm_s390_sca_set_mtcr(vcpu->kvm);
> 
> We set the MTCR in the vcpu create. Does it also make sense to set it in kvm_arch_vcpu_destroy?
> 
> [...]
>> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
>> index 12c464c7cddf..77a692238585 100644
>> --- a/arch/s390/kvm/priv.c
>> +++ b/arch/s390/kvm/priv.c
>> @@ -873,10 +873,13 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
> [...]
>> +       case 15:
>> +               trace_kvm_s390_handle_stsi(vcpu, fc, sel1, sel2, operand2);
>> +               insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2);
>> +               return -EREMOTE;
> 
> Maybe the API documentation should clearly note that once you turn on KVM_CAP_S390_CPU_TOPOLOGY, you will get exits to userspace for STSI 15.x.y, regardless of whether KVM_CAP_S390_USER_STSI is on or off.

Humm, right, I must change this, it is not right to have STSI(15) but 
not STSI([123])

I will also have two other changes in this patch, the locking and add a 
check for PV on STSI(15)

So I will respin in a short time.


> 
> Other than that, looks good, hence:
> 
> Reviewed-by: Nico Boehr <nrb@...ux.ibm.com>
> 

-- 
Pierre Morel
IBM Lab Boeblingen