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

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Date: Thu, 27 Jun 2024 20:47:13 +0200
From: Christoph Schlameuss <schlameuss@...ux.ibm.com>
To: Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini
 <pbonzini@...hat.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 Thu, 27 Jun 2024 14:32:51 +0200
Janosch Frank <frankja@...ux.ibm.com> wrote:

> 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.

I do also have a test case for this specifically, but it depends on the
base fixture. So I would send it together with that soon.

Christoph