linux-kernel - Re: [PATCH] s390/kvm: Reject memory region operations for ucontrol VMs

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Date: Thu, 27 Jun 2024 14:32:51 +0200
From: Janosch Frank <frankja@...ux.ibm.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
        Christoph Schlameuss <schlameuss@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH] s390/kvm: Reject memory region operations for ucontrol
 VMs

On 6/27/24 13:53, Paolo Bonzini wrote:
> On Mon, Jun 24, 2024 at 11:59 AM Christoph Schlameuss
> <schlameuss@...ux.ibm.com> wrote:
>>
>> This change rejects the KVM_SET_USER_MEMORY_REGION and
>> KVM_SET_USER_MEMORY_REGION2 ioctls when called on a ucontrol VM.
>> This is neccessary since ucontrol VMs have kvm->arch.gmap set to 0 and
>> would thus result in a null pointer dereference further in.
>> Memory management needs to be performed in userspace and using the
>> ioctls KVM_S390_UCAS_MAP and KVM_S390_UCAS_UNMAP.
>>
>> Also improve s390 specific documentation for KVM_SET_USER_MEMORY_REGION
>> and KVM_SET_USER_MEMORY_REGION2.
> 
> Would be nice to have a selftest for ucontrol VMs, too... just saying :)
> 
> Paolo
> 

Already in the works, he just hasn't posted it yet :)
We did do a couple rounds of internal feedback on the tests first.