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

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Message-ID: <CABgObfYxZZdwe94u7OvHPUx+u4fDEJLnBEQbk1hdYs_Zy0D2hA@mail.gmail.com>
Date: Thu, 27 Jun 2024 13:53:24 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: 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>, Janosch Frank <frankja@...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 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