From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45818 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728076AbgEEOBG (ORCPT ); Tue, 5 May 2020 10:01:06 -0400 Subject: Re: [PATCH v2 1/1] fs/splice: add missing callback for inaccessible pages 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 Message-ID: <45bc81bb-8765-ffff-6e47-8ee9702c8bcd@de.ibm.com> Date: Tue, 5 May 2020 16:00:10 +0200 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 Sender: linux-s390-owner@vger.kernel.org List-ID: 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 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?