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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 0DA84C47254 for ; Fri, 1 May 2020 10:55:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD41421973 for ; Fri, 1 May 2020 10:55:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588330527; bh=erC6W5Is3Nh/oL4QwwTvkse8Vyv5xbMSlz9NG80pnSs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=szqSoBXfMocDP92oYDbFUrcaRlSNKSU11RnPf99LW1qkhBDjvsbzh3aV4lbapIt01 TOapY+XfZ4Qfgl6aNNyn8BfcwuiOkyIM804sOnSOtV+3kgR49AZjEeThLVVc84cI/r XofXGIZA1WwxXytYwXvetxC0dlL164oPeLhxBeGc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728588AbgEAKzY (ORCPT ); Fri, 1 May 2020 06:55:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:51236 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728352AbgEAKzW (ORCPT ); Fri, 1 May 2020 06:55:22 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E06052166E; Fri, 1 May 2020 10:55:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588330522; bh=erC6W5Is3Nh/oL4QwwTvkse8Vyv5xbMSlz9NG80pnSs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uEKrn4o5840WtXxkC9WrJ17O5Jlu2T5837fDfIhIeL2APjwSqIXoIC8mLpye/1y/9 13sLP6s7aik7eVuQOxVCXsjN5lnl3XoM4n3Zye2tx6gXqZmiZX0iAeWLo/MDIQpnJQ aytWAXjD/jPWwGbEdZVKarybkBxRoKVTfPxdNT4E= Date: Fri, 1 May 2020 12:55:20 +0200 From: Greg KH To: Mark Rutland Cc: Jeremy Linton , linux-usb@vger.kernel.org, stern@rowland.harvard.edu, git@thegavinli.com, jarkko.sakkinen@linux.intel.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] usb: usbfs: correct kernel->user page attribute mismatch Message-ID: <20200501105520.GA1434711@kroah.com> References: <20200430211922.929165-1-jeremy.linton@arm.com> <20200501070500.GA887524@kroah.com> <20200501103712.GA51954@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200501103712.GA51954@C02TD0UTHF1T.local> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Fri, May 01, 2020 at 11:37:12AM +0100, Mark Rutland wrote: > On Fri, May 01, 2020 at 09:05:00AM +0200, Greg KH wrote: > > On Thu, Apr 30, 2020 at 04:19:22PM -0500, Jeremy Linton wrote: > > > On arm64, and possibly other architectures, requesting > > > IO coherent memory may return Normal-NC if the underlying > > > hardware isn't coherent. If these pages are then > > > remapped into userspace as Normal, that defeats the > > > purpose of getting Normal-NC, as well as resulting in > > > mappings with differing cache attributes. > > > > What is "Normal-NC"? > > Arm terminology for "Normal Non-Cacheable"; it might be better to say > something like: > > On some architectures (e.g. arm64) an IO coherent mapping may use > non-cachable attributes if the relevant device is cache coherent. > If userspace mappings are cacheable, these may not be coherent with > non-cacheable mappings. On arm64 this is the case for Normal-NC and > Normal (cacheable) mappings. That's better, but it doesn't answer any of my other questions on this patch :) thanks, greg k-h