linux-kernel - Re: [PATCH v3 03/14] KVM: s390: pv: leak the ASCE page when destroy fails

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Date:   Fri, 6 Aug 2021 09:31:54 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     cohuck@...hat.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ulrich.Weigand@...ibm.com
Subject: Re: [PATCH v3 03/14] KVM: s390: pv: leak the ASCE page when destroy
 fails

On 04.08.21 17:40, Claudio Imbrenda wrote:
> When a protected VM is created, the topmost level of page tables of its
> ASCE is marked by the Ultravisor; any attempt to use that memory for
> protected virtualization will result in failure.
> 
> Only a successful Destroy Configuration UVC will remove the marking.
> 
> When the Destroy Configuration UVC fails, the topmost level of page
> tables of the VM does not get its marking cleared; to avoid issues it
> must not be used again.
> 
> Since the page becomes in practice unusable, we set it aside and leak it.

Instead of leaking, can't we add it to some list and try again later? Or 
do we only expect permanent errors?

Also, we really should bail out loud (pr_warn) to tell the admin that 
something really nasty is going on.

-- 
Thanks,

David / dhildenb