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

David Hildenbrand
2021-08-06T11:39:15Z

On 06.08.21 11:32, Claudio Imbrenda wrote:
> On Fri, 6 Aug 2021 09:31:54 +0200
> David Hildenbrand <david@redhat.com> wrote:
>
>> 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?
>
> once the secure VM has been destroyed unsuccessfully, there is nothing
> that can be done, this is a permanent error
>
>> Also, we really should bail out loud (pr_warn) to tell the admin that
>> something really nasty is going on.
>
> when a destroy secure VM UVC fails, there are already other warnings
> printed, no need to add one more
>

Okay, makes sense then to me, thanks! Might be worth adding some of that
info to the patch description.

--
Thanks,

David / dhildenb