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[91.12.97.4]) by smtp.gmail.com with ESMTPSA id o24sm9843900wmm.37.2021.08.06.00.31.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Aug 2021 00:31:55 -0700 (PDT) Subject: Re: [PATCH v3 03/14] KVM: s390: pv: leak the ASCE page when destroy fails To: Claudio Imbrenda , kvm@vger.kernel.org Cc: 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 References: <20210804154046.88552-1-imbrenda@linux.ibm.com> <20210804154046.88552-4-imbrenda@linux.ibm.com> From: David Hildenbrand Organization: Red Hat Message-ID: <6b75cc71-b996-cf3d-ce57-dbcd475ebc3a@redhat.com> Date: Fri, 6 Aug 2021 09:31:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210804154046.88552-4-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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