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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 2C81FC4BA34 for ; Fri, 13 Dec 2019 20:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6114A24758 for ; Fri, 13 Dec 2019 20:39:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="ThBk7Cyj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728340AbfLMQi0 (ORCPT ); Fri, 13 Dec 2019 11:38:26 -0500 Received: from mail.skyhub.de ([5.9.137.197]:36212 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727480AbfLMQi0 (ORCPT ); Fri, 13 Dec 2019 11:38:26 -0500 Received: from zn.tnic (p200300EC2F0A5A00E05EA1F3CB5927A8.dip0.t-ipconnect.de [IPv6:2003:ec:2f0a:5a00:e05e:a1f3:cb59:27a8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id E4ADC1EC0D05; Fri, 13 Dec 2019 17:38:24 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1576255105; 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: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=U1lMKBvl7t0uA7vs1lBWLnqmt5G1DUAC7gAqYkIurz4=; b=ThBk7Cyjp8/zS0rF3ChUwzKW8vplJXRdLqiiwOMh2PEF1rzp3FQ6UPNT9Rps9Cv9mUvsuI ydEWJF7+LBav3DByHM0gMVDhPVT3bwBmu+7UtOH+qnHOc4gCtyaEckVdWsZTmPcwOwuaWk AVbhufKMZN+m29Je8YwfYkToyp4cIjE= Date: Fri, 13 Dec 2019 17:38:18 +0100 From: Borislav Petkov To: Baoquan He Cc: Masayoshi Mizuma , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Masayoshi Mizuma , linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 4/4] x86/mm/KASLR: Adjust the padding size for the direct mapping. Message-ID: <20191213163818.GB25899@zn.tnic> References: <20191115144917.28469-1-msys.mizuma@gmail.com> <20191115144917.28469-5-msys.mizuma@gmail.com> <20191212201916.GL4991@zn.tnic> <20191213132850.GG28917@MiWiFi-R3L-srv> <20191213141543.GA25899@zn.tnic> <20191213145448.GH28917@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191213145448.GH28917@MiWiFi-R3L-srv> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 13, 2019 at 10:54:48PM +0800, Baoquan He wrote: > On 12/13/19 at 03:15pm, Borislav Petkov wrote: > > On Fri, Dec 13, 2019 at 09:28:50PM +0800, Baoquan He wrote: > > > In Documentation/x86/x86_64/mm.rst, the physical memory regions mapping > > > with page_offset is called as the direct mapping of physical memory. > > > > The fact that it happens to compute the *first* region's size, which > > *happens* to be the direct mapping of all physical memory is immaterial > > here. > > > > It is actually causing more confusion in an already complex piece of > > code. You can call this function just as well > > > > calc_region_size() > > > > which won't confuse readers. Because all you care about here is the > > region's size - not which region it is. > > Won't calc_region_size be too generic? We also have vmalloc and vmemmap, > and here we are specifically calculating the direct mapping of physical > memory. It sounds like you didn't read what I wrote above so read it again pls. > If not knowing the max address to cover all the possible hotplugged > memory, later memory hotplug will fail. You don't have to state the obvious - I can see that in the code. So let me ask you differently: can the parsing of the SRAT table happen shortly before kernel_randomize_memory() *without* adding all that gunk to the compressed stage, and without adding the boot_params member and done only for memory hot_add machines? -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette