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Tue, 05 May 2020 14:00:17 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 045E0C281507738 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 5 May 2020 14:00:12 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0FDC611C074; Tue, 5 May 2020 14:00:12 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 121BB11C07F; Tue, 5 May 2020 14:00:11 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.145.49.139]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 5 May 2020 14:00:10 +0000 (GMT) Subject: Re: [PATCH v2 1/1] fs/splice: add missing callback for inaccessible pages To: Dave Hansen , Ulrich Weigand Cc: Claudio Imbrenda , viro@zeniv.linux.org.uk, david@redhat.com, akpm@linux-foundation.org, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, jhubbard@nvidia.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, jack@suse.cz, kirill@shutemov.name, peterz@infradead.org, sean.j.christopherson@intel.com, Ulrich.Weigand@de.ibm.com References: <20200430143825.3534128-1-imbrenda@linux.ibm.com> <1a3f5107-9847-73d4-5059-c6ef9d293551@de.ibm.com> <3d379d9e-241c-ef3b-dcef-20fdd3b8740d@de.ibm.com> <20200504134154.GA21001@oc3748833570.ibm.com> <231da2f1-a6ef-0cf9-7f57-95e8b925997b@intel.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <231da2f1-a6ef-0cf9-7f57-95e8b925997b@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-05-05_08:2020-05-04,2020-05-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 malwarescore=0 suspectscore=0 priorityscore=1501 spamscore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 mlxlogscore=999 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050105 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05.05.20 14:34, Dave Hansen wrote:[...] >> I'm not sure what exactly the requirements for your use case are; if those >> are significantly differently, maybe we can work together to find an >> approach that works for both? > > I'm actually trying to figure out what to do with AMD's SEV. The > current state isn't great and, for instance, allows userspace to read > guest ciphertext. But, the pages come and go out of the encrypted state > at the behest of the guest, and the kernel needs *some* mapping for the > pages to do things like instruction emulation. > > I started looking at s390 because someone said there was a similar > problem there and suggested the hooks might work. I couldn't figure out > how they worked comprehensively on s390, and that's how we got here. We are certainly not married to our approach. I would happily extend/change this to anything that works for your case and the s390 case. So can you outline your requirements a bit more?