linux-kernel - Re: [PATCH v12 3/3] KVM: s390: resetting the Topology-Change-Report

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Message-ID: <d62d2844-1d3b-4a0a-73dc-8ed961d9e22e@linux.ibm.com>
Date:   Thu, 14 Jul 2022 10:37:21 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Janosch Frank <frankja@...ux.ibm.com>,
        Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
        kvm@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        borntraeger@...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,
        nrb@...ux.ibm.com
Subject: Re: [PATCH v12 3/3] KVM: s390: resetting the Topology-Change-Report



On 7/13/22 11:01, Janosch Frank wrote:
> On 7/12/22 13:17, Pierre Morel wrote:
>>
>>
>> On 7/12/22 10:47, Janis Schoetterl-Glausch wrote:
>>> On 7/12/22 09:24, Pierre Morel wrote:
>>>>
>>>>

...

>> kernel.
>>
>> In userland we check any wrong selector before the instruction goes back
>> to the guest.
> 
> I opt for passing the lower selectors down for QEMU to handle.

OK

> 
>>
>>> But that's only relevant if STSI can be extended without a 
>>> capability, which is why I asked about that.
>>
>> Logicaly any change, extension, in the architecture should be signaled
>> by a facility bit or something.
>>
>>>
>>>> Even testing the facility or PV in the kernel is for my opinion 
>>>> arguable in the case we do not do any treatment in the kernel.
> 
> That's actually a good point.
> 
> New instruction interceptions for PV will need to be enabled by KVM via 
> a switch somewhere since the UV can't rely on the fact that KVM will 
> correctly handle it without an enablement.
> 
> 
> So please remove the pv check

OK

> 

...

>>>>>>     +static int kvm_s390_set_topology(struct kvm *kvm, struct 
>>>>>> kvm_device_attr *attr)
>>>>>
>>>>> kvm_s390_set_topology_changed maybe?
>>>>> kvm_s390_get_topology_changed below then.
> 
> kvm_s390_set_topology_change_indication
> 
> It's long but it's rarely used.
> Maybe shorten topology to "topo"

OK
I use
kvm_s390_get_topo_change_indication()


Thanks.

Regards,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen