From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753210AbdIRS4U (ORCPT ); Mon, 18 Sep 2017 14:56:20 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:43536 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753075AbdIRS4S (ORCPT ); Mon, 18 Sep 2017 14:56:18 -0400 Subject: Re: [BACKPORT] swiotlb-xen: implement xen_swiotlb_dma_mmap callback To: Stefano Stabellini , Greg KH References: <20170916012352.GA21774@kroah.com> Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, julien.grall@arm.com, jgross@suse.com From: Boris Ostrovsky Message-ID: <20abb053-64fc-c7a3-066f-6d1491f13108@oracle.com> Date: Mon, 18 Sep 2017 14:55:54 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/18/2017 02:08 PM, 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. This is a nop for x86 so it's safe from that perspective. I can't find mmap op for ARM though (xen_get_dma_ops(dev)->mmap). -boris