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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 800BCC388F7 for ; Sun, 8 Nov 2020 01:16:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDE45206A4 for ; Sun, 8 Nov 2020 01:16:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=agner.ch header.i=@agner.ch header.b="DsC/Mq/X" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728766AbgKHBQn (ORCPT ); Sat, 7 Nov 2020 20:16:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725838AbgKHBQm (ORCPT ); Sat, 7 Nov 2020 20:16:42 -0500 Received: from mail.kmu-office.ch (mail.kmu-office.ch [IPv6:2a02:418:6a02::a2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9360AC0613CF for ; Sat, 7 Nov 2020 17:16:42 -0800 (PST) Received: from webmail.kmu-office.ch (unknown [IPv6:2a02:418:6a02::a3]) by mail.kmu-office.ch (Postfix) with ESMTPSA id 44BBE5C0578; Sun, 8 Nov 2020 02:16:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=agner.ch; s=dkim; t=1604798198; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dLE43ZLA8hp6UktmPV/LfyXxESj/KMWUrBP1RF1ENVY=; b=DsC/Mq/XXB7fYqz/csDP6ii7P2ZroqESQeOI2mC9ux6+0qR/orbNMOgN1vhjTJA+VtOB9C bFCraFNMPo/XNjKrub1zkWK/TaphtteLuzCx5zQy3p6w16pMDvDWVUIIJrbRiMsDE4s+px ijemFdXgotntVsYjiqoCT0X9Zs6/0D4= MIME-Version: 1.0 Date: Sun, 08 Nov 2020 02:16:37 +0100 From: Stefan Agner To: Andrew Morton Cc: minchan@kernel.org, ngupta@vflare.org, sergey.senozhatsky.work@gmail.com, sjenning@linux.vnet.ibm.com, gregkh@linuxfoundation.org, arnd@arndb.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS In-Reply-To: <20201107165645.1b139b595b6b64feaca61bcb@linux-foundation.org> References: <20201107165645.1b139b595b6b64feaca61bcb@linux-foundation.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: X-Sender: stefan@agner.ch Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-11-08 01:56, Andrew Morton wrote: > On Sat, 7 Nov 2020 16:22:06 +0100 Stefan Agner wrote: > >> Most architectures define MAX_PHYSMEM_BITS in asm/sparsemem.h and don't >> include it in asm/pgtable.h. Include asm/sparsemem.h directly to get >> the MAX_PHYSMEM_BITS define on all architectures. >> >> This fixes a crash when accessing zram on 32-bit ARM platform with LPAE and >> more than 4GB of memory: >> Unable to handle kernel NULL pointer dereference at virtual address 00000000 > > Mysterious. Presumably without this include, some compilation unit is > picking up the wrong value of MAX_PHYSMEM_BITS? But I couldn't > actually see where/how this occurs. Can you please explain further? Not sure if I got that right, but from what I understand if MAX_PHYSMEM_BITS is not set in mm/zsmalloc.c it will set MAX_PHYSMEM_BITS to BITS_PER_LONG. And this is 32-bit, too short when LPAE is in use... -- Stefan