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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 34863C43381 for ; Tue, 12 Mar 2019 07:13:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0F387214AE for ; Tue, 12 Mar 2019 07:13:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727348AbfCLHNS (ORCPT ); Tue, 12 Mar 2019 03:13:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36262 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726614AbfCLHNS (ORCPT ); Tue, 12 Mar 2019 03:13:18 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4259A308125D; Tue, 12 Mar 2019 07:13:18 +0000 (UTC) Received: from localhost (ovpn-204-138.brq.redhat.com [10.40.204.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 770EC60A9A; Tue, 12 Mar 2019 07:13:15 +0000 (UTC) Date: Tue, 12 Mar 2019 08:13:14 +0100 From: Stanislaw Gruszka To: Rosen Penev Cc: Joerg Roedel , Lorenzo Bianconi , linux-wireless , Samuel Sieb , Alexander Duyck , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, jan.viktorin@gmail.com Subject: Re: MT76x2U crashes XHCI driver on AMD Ryzen system Message-ID: <20190312071314.GB2483@redhat.com> References: <20190226103450.GA2989@redhat.com> <20190226104413.GH20740@8bytes.org> <20190226112407.GB2989@redhat.com> <20190228090411.GA24938@redhat.com> <20190228104223.GA2749@redhat.com> <20190228121948.GD6072@redhat.com> <20190228134029.GC1594@8bytes.org> <20190304071037.GA2787@redhat.com> <20190311084319.GA3310@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190311084319.GA3310@redhat.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 12 Mar 2019 07:13:18 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Mon, Mar 11, 2019 at 09:43:19AM +0100, Stanislaw Gruszka wrote: > > > However after fixing that mt76usb still did not work. To make things > > > work we had to change rx frag size from 2048 to PAGE_SIZE and change > > > virt_to_head_page() to virt_to_page() when setting SG's. > > > > > I think I understand why first change was needed. If we do 2 separate > > > dma maps of 2 different buffers in single page i.e (PAGE + off=0 > > > and PAGE + off=2048) it causes problem. So either map_sg() return > > > error which mt76usb does not handle correctly or there is issue > > > in AMD IOMMU because two dma maps use the same page. > > Any comment on that? Is fine or not to do 2 or more dma mappings > within the same single page on AMD IOMMU? If not, is there any > mechanism for drivers to find out about this limitation to prevent > to prepare wrong SG buffers? FTR: it was confirmed by Jan (bug reporter) the 2 or more dma mappings within single page works with AMD IOMMU. Most likely it was needed previously to workaround this sg->offset problem until proper fix to AMD IOMMU was applied. Stanislaw