Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755704AbdIRSIG (ORCPT ); Mon, 18 Sep 2017 14:08:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:35374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752727AbdIRSIE (ORCPT ); Mon, 18 Sep 2017 14:08:04 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E5E3218F8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=sstabellini@kernel.org Date: Mon, 18 Sep 2017 11:08:03 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-X260 To: Greg KH cc: Stefano Stabellini , stable@vger.kernel.org, linux-kernel@vger.kernel.org, julien.grall@arm.com, jgross@suse.com, boris.ostrovsky@oracle.com Subject: Re: [BACKPORT] swiotlb-xen: implement xen_swiotlb_dma_mmap callback In-Reply-To: <20170916012352.GA21774@kroah.com> Message-ID: References: <20170916012352.GA21774@kroah.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1807 Lines: 45 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.