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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,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 35DBDC43468 for ; Sun, 20 Sep 2020 06:23:33 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C19F92085B for ; Sun, 20 Sep 2020 06:23:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ZdXKJXZG"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="yd7i2Kht" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C19F92085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id ACA1F6E185; Sun, 20 Sep 2020 06:23:31 +0000 (UTC) Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by gabe.freedesktop.org (Postfix) with ESMTPS id 32EF16E185; Sun, 20 Sep 2020 06:23:30 +0000 (UTC) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1600583007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7fzEIVZ8tkjS2ndcSNVbu7zYvMlAYQ/NWyoKHxP3faw=; b=ZdXKJXZGwHl2KR4hH2q5cUf4dfgyefKiq5FJK4CdaiUzjuDw/zsfzyDwUT0Vb3vxnFMmA2 GbGWdXGNam/BxDVayB/9W9lKW9cEGTy4k40j+g76SxOFKgyaP4kz+dJNXxDya0A6vacAHQ etbQkUBwH/pk7aVUdpmHO5hYMDrDQDP5KgAuzWF1TeBFDWPD7hNOa95TYtIkpNlkk7xqPo YZDmeBiMP6cP8bfVBIDyjT3CMK5xsUBeFdgoJYUZ63lHnZ5f4NanBw5QbC7HkoYRGwgBsy Bsz/o+mfvaeq05vAqvejTR9EViDozt0cf4n5wRrzHjQfCFUXuG/KuqeDB61mqg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1600583007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7fzEIVZ8tkjS2ndcSNVbu7zYvMlAYQ/NWyoKHxP3faw=; b=yd7i2KhtoQQ4HuYBfV4K2iDNHIVcqLD+eOCjOAMiHylcYwCzvC7AWTYk8VGrY+iNFLAu2j 3+A+8QdYt6q7wFBw== To: Daniel Vetter In-Reply-To: References: <20200919091751.011116649@linutronix.de> Date: Sun, 20 Sep 2020 08:23:26 +0200 Message-ID: <87pn6hc6g1.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juri Lelli , Peter Zijlstra , Benjamin Herrenschmidt , Sebastian Andrzej Siewior , dri-devel , linux-mips@vger.kernel.org, Ben Segall , Max Filippov , Guo Ren , sparclinux@vger.kernel.org, Vincent Chen , Will Deacon , Ard Biesheuvel , "open list:GENERIC INCLUDE/A..." , Herbert Xu , Michael Ellerman , X86 ML , Russell King , linux-csky@vger.kernel.org, David Airlie , Mel Gorman , arcml , linux-xtensa@linux-xtensa.org, Paul McKenney , intel-gfx , linuxppc-dev , Steven Rostedt , Linus Torvalds , Dietmar Eggemann , Linux ARM , Chris Zankel , Michal Simek , Thomas Bogendoerfer , Nick Hu , Linux-MM , Vineet Gupta , LKML , Arnd Bergmann , Paul Mackerras , Andrew Morton , Daniel Bristot de Oliveira , "David S. Miller" , Greentime Hu Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Sat, Sep 19 2020 at 12:37, Daniel Vetter wrote: > On Sat, Sep 19, 2020 at 12:35 PM Daniel Vetter wrote: >> I think it should be the case, but I want to double check: Will >> copy_*_user be allowed within a kmap_temporary section? This would >> allow us to ditch an absolute pile of slowpaths. > > (coffee just kicked in) copy_*_user is ofc allowed, but if you hit a > page fault you get a short read/write. This looks like it would remove > the need to handle these in a slowpath, since page faults can now be > served in this new kmap_temporary sections. But this sounds too good > to be true, so I'm wondering what I'm missing. In principle we could allow pagefaults, but not with the currently proposed interface which can be called from any context. Obviously if called from atomic context it can't handle user page faults. In theory we could make a variant which does not disable pagefaults, but that's what kmap() already provides. Thanks, tglx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx