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Fri, 6 Aug 2021 09:34:51 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 52A704204B; Fri, 6 Aug 2021 09:34:51 +0000 (GMT) Received: from p-imbrenda (unknown [9.145.6.208]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 6 Aug 2021 09:34:51 +0000 (GMT) Date: Fri, 6 Aug 2021 11:32:44 +0200 From: Claudio Imbrenda To: David Hildenbrand Cc: kvm@vger.kernel.org, cohuck@redhat.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Ulrich.Weigand@de.ibm.com Subject: Re: [PATCH v3 03/14] KVM: s390: pv: leak the ASCE page when destroy fails Message-ID: <20210806113244.4d0712d2@p-imbrenda> In-Reply-To: <6b75cc71-b996-cf3d-ce57-dbcd475ebc3a@redhat.com> References: <20210804154046.88552-1-imbrenda@linux.ibm.com> <20210804154046.88552-4-imbrenda@linux.ibm.com> <6b75cc71-b996-cf3d-ce57-dbcd475ebc3a@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 383vxRM3eEFQr1HkCojJn6nzT7c4RSec X-Proofpoint-ORIG-GUID: 7GKBbEyUDX3-Aax2ZTLr8Ea1xTGqDHn1 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-06_02:2021-08-05,2021-08-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=999 clxscore=1015 mlxscore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108060067 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Aug 2021 09:31:54 +0200 David Hildenbrand 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