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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 F20FBC433E2 for ; Tue, 15 Sep 2020 07:11:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4DD62080C for ; Tue, 15 Sep 2020 07:11:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600153871; bh=BGQ3eCEwFUe6AJJmnaDMEuJg2cqiX9jtXT/M/+4eiks=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=hy2TLnZv4grSyE6sg26PdZ5OyxHp1mG1lzI1XTRHAH60viph5XK74admhgY+VMgy1 rumflPT43D9+rIEauNTqa1nh7c12wnx0PGyOr/ZRNZTvLN/JbUWhEYLa+4wlqUAJj6 6umRmd47wur4RFfCCPZXlPzh1J90vfdH1hmVXUPY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726153AbgIOHLH (ORCPT ); Tue, 15 Sep 2020 03:11:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:41644 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726091AbgIOHKx (ORCPT ); Tue, 15 Sep 2020 03:10:53 -0400 Received: from mail-oi1-f179.google.com (mail-oi1-f179.google.com [209.85.167.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3A908206B5; Tue, 15 Sep 2020 07:10:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600153852; bh=BGQ3eCEwFUe6AJJmnaDMEuJg2cqiX9jtXT/M/+4eiks=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Hy57j0JDynjYyG6P78cB/X1ne7QBpDvOxYkzQbbuaNpIX3IdS2n1KyHL4x5/bi5+S 3laCU23JHUdHfWt+siVuRf3ieBtU/E7sRcsZO7DqQX+xUgilE39x5D8ltzHwfHf3yc kDP0LT1pbCysA/0jbWpFreFar91CV8K4FxLz2ENA= Received: by mail-oi1-f179.google.com with SMTP id x14so2717270oic.9; Tue, 15 Sep 2020 00:10:52 -0700 (PDT) X-Gm-Message-State: AOAM5330TOH9YEifFZ64/Qa+2yl+UoDyGZVYlpx1mPoBb5PezPMQpdYo 4lEYtfjLvgzu76BhwPuQnuEOwy+1wZn264Rvr8c= X-Google-Smtp-Source: ABdhPJy2V/mnAsBclEEUOHdahMPoNIrScUu4KK+F3G+7suXAqZOb+5SpImHNQzKwxItMwxyIy05XxZZ+k4f/AYv1lvw= X-Received: by 2002:a54:4517:: with SMTP id l23mr2478818oil.174.1600153851496; Tue, 15 Sep 2020 00:10:51 -0700 (PDT) MIME-Version: 1.0 References: <20200914204209.256266093@linutronix.de> <871rj4owfn.fsf@nanos.tec.linutronix.de> <20200915033024.GB25789@gondor.apana.org.au> <20200915070523.GA26629@gondor.apana.org.au> In-Reply-To: <20200915070523.GA26629@gondor.apana.org.au> From: Ard Biesheuvel Date: Tue, 15 Sep 2020 10:10:40 +0300 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally To: Herbert Xu Cc: Linus Torvalds , Thomas Gleixner , LKML , Linux Crypto Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 15 Sep 2020 at 10:05, Herbert Xu wrote: > > On Mon, Sep 14, 2020 at 11:55:53PM -0700, Linus Torvalds wrote: > > > > Maybe we could hide it behind a debug option, at least. > > > > Or, alterantively, introduce a new "debug_preempt_count" that doesn't > > actually disable preemption, but warns about actual sleeping > > operations.. > > I'm more worried about existing users of kmap_atomic relying on > the preemption disabling semantics. Short of someone checking > on every single instance (and that would include derived cases > such as all users of sg miter), I think the safer option is to > create something brand new and then migrate the existing users > to it. Something like > > static inline void *kmap_atomic_ifhigh(struct page *page) > { > if (PageHighMem(page)) > return kmap_atomic(page); > return page_address(page); > } > > static inline void kunmap_atomic_ifhigh(struct page *page, void *addr) > { > if (PageHighMem(page)) > kunmap_atomic(addr); > } > But we would still need to check all users of SG miter before we could move it to this interface.