Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752394AbdIVMPc (ORCPT ); Fri, 22 Sep 2017 08:15:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:47460 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752296AbdIVMPa (ORCPT ); Fri, 22 Sep 2017 08:15:30 -0400 Subject: Re: [BACKPORT] swiotlb-xen: implement xen_swiotlb_dma_mmap callback To: Stefano Stabellini , Greg KH Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, julien.grall@arm.com, boris.ostrovsky@oracle.com References: <20170916012352.GA21774@kroah.com> From: Juergen Gross Message-ID: <752f8705-9129-b940-2f88-bfe696b14b63@suse.com> Date: Fri, 22 Sep 2017 14:15:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1927 Lines: 52 On 18/09/17 20:08, Stefano Stabellini wrote: > On Fri, 15 Sep 2017, Greg KH wrote: >> On Thu, Sep 14, 2017 at 04:23:05PM -0700, Stefano Stabellini wrote: >>> Hi all, >>> >>> We are getting reports from Xen on ARM users about DMA issues. The >>> problem is that the commit below >>> (7e91c7df29b5e196de3dc6f086c8937973bd0b88) is necessary to support mmap >>> on Xen on ARM. It is self-contained and doesn't affect anything outside >>> of Xen on ARM, so I think is a good candidate for backporting. It went >>> upstream in 4.11. >> >> But it's a new feature, right? How does that fit the stable kernel >> rules? > > It implements a previously unimplemented function (mmap), although it > calls the generic functions to do it. Yes, I agree with you that it > can be classified as a new feature. If that is against the stable kernel > rules, then please discard this request. > > FYI the reason why it didn't raise a flag in my mind is that users > reported something like "unhandled alignment fault (11) at > 0xffffa6048080, esr 0x92000061", which really looks more like a bug. > > >>> Could you please backport the following commit: >>> >>> commit 7e91c7df29b5e196de3dc6f086c8937973bd0b88 >>> Author: Stefano Stabellini >>> Date: Tue Feb 7 19:58:02 2017 +0200 >>> >>> swiotlb-xen: implement xen_swiotlb_dma_mmap callback >>> >>> This function creates userspace mapping for the DMA-coherent memory. >>> >>> to the stable trees up until 3.14? >>> >>> >>> Because of 00085f1efa387a8ce100e3734920f7639c80caa3 "dma-mapping: use >>> unsigned long for dma_attrs", the appended patch (to be applied on top) >>> is required for trees older than 4.8. >> >> What does the kvm maintainers think about this? > > That would be the Xen maintainers right? In that case, Boris, Juergen, > please let us know what you think. > I have no specific preference. Juergen