From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 764CCC433E3 for ; Mon, 27 Jul 2020 09:21:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D27020759 for ; Mon, 27 Jul 2020 09:21:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726846AbgG0JVt convert rfc822-to-8bit (ORCPT ); Mon, 27 Jul 2020 05:21:49 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2526 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726263AbgG0JVt (ORCPT ); Mon, 27 Jul 2020 05:21:49 -0400 Received: from lhreml710-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id E39C5FA1E84846A6F6C9; Mon, 27 Jul 2020 10:21:47 +0100 (IST) Received: from localhost (10.52.121.176) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Mon, 27 Jul 2020 10:21:47 +0100 Date: Mon, 27 Jul 2020 10:20:24 +0100 From: Jonathan Cameron To: Logan Gunthorpe CC: Bjorn Helgaas , Alex Deucher , LKML , Linux PCI , Bjorn Helgaas , Christian =?ISO-8859-1?Q?K=F6nig?= , Huang Rui , Andrew Maier , "H. Peter Anvin" , Eric Wehage , "Alex Umansky" Subject: Re: [PATCH] PCI/P2PDMA: Add AMD Zen 2 root complex to the list of allowed bridges Message-ID: <20200727102024.00005f8b@Huawei.com> In-Reply-To: <59b68da4-cd3c-bf65-6654-02d4feaede27@deltatee.com> References: <20200724150641.GA1518875@bjorn-Precision-5520> <59b68da4-cd3c-bf65-6654-02d4feaede27@deltatee.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8BIT X-Originating-IP: [10.52.121.176] X-ClientProxiedBy: lhreml704-chm.china.huawei.com (10.201.108.53) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, 24 Jul 2020 09:56:39 -0600 Logan Gunthorpe wrote: > [+cc Jonathan] > > On 2020-07-24 9:06 a.m., Bjorn Helgaas wrote: > > On Thu, Jul 23, 2020 at 02:10:52PM -0600, Logan Gunthorpe wrote: > >> On 2020-07-23 1:57 p.m., Bjorn Helgaas wrote: > >>> On Thu, Jul 23, 2020 at 02:01:17PM -0400, Alex Deucher wrote: > >>>> On Thu, Jul 23, 2020 at 1:43 PM Logan Gunthorpe wrote: > >>>>> > >>>>> The AMD Zen 2 root complex (Starship/Matisse) was tested for P2PDMA > >>>>> transactions between root ports and found to work. Therefore add it > >>>>> to the list. > >>>>> > >>>>> Signed-off-by: Logan Gunthorpe > >>>>> Cc: Bjorn Helgaas > >>>>> Cc: Christian König > >>>>> Cc: Huang Rui > >>>>> Cc: Alex Deucher > >>>> > >>>> Starting with Zen, all AMD platforms support P2P for reads and writes. > >>> > >>> What's the plan for getting out of the cycle of "update this list for > >>> every new chip"? Any new _DSMs planned, for instance? > >> > >> Well there was an effort to add capabilities in the PCI spec to describe > >> this but, as far as I know, they never got anywhere, and hardware still > >> doesn't self describe with this. > > > > Any idea what happened? Is there hope for the future? I'm really not > > happy about signing up for open-ended device-specific patches like > > this. It's certainly not in the plug and play spirit that has made > > PCI successful. I know, preaching to the choir here. > > Agreed, though I'm not really hooked into the PCI SIG. The last email I > got about this was an RFC from Jonathan Cameron in late 2018. I've CC'd > him here, maybe he'll have a bit more insight. For non technical reasons, you can probably figure out, that particular ECR stalled. Unfortunately I can't directly provide info on any newer discussions. Eric, could you perhaps find out if there is anything we can share? This is the same question of trying to find a way to avoid white listing root complexes that can do peer 2 peer that would have been covered by your Advanced Peer to Peer Capabilities ECR. Thanks, Jonathan > > Logan