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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham 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 AB259C433F5 for ; Fri, 31 Aug 2018 06:11:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B82920837 for ; Fri, 31 Aug 2018 06:11:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B82920837 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727438AbeHaKRE (ORCPT ); Fri, 31 Aug 2018 06:17:04 -0400 Received: from mga03.intel.com ([134.134.136.65]:4541 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727197AbeHaKRD (ORCPT ); Fri, 31 Aug 2018 06:17:03 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Aug 2018 23:11:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,309,1531810800"; d="scan'208";a="66544050" Received: from shbuild888.sh.intel.com (HELO localhost) ([10.239.146.239]) by fmsmga007.fm.intel.com with ESMTP; 30 Aug 2018 23:10:51 -0700 Date: Fri, 31 Aug 2018 14:15:19 +0800 From: Feng Tang To: Thomas Gleixner Cc: Michal Hocko , Peter Zijlstra , linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar , "H . Peter Anvin" , Yinghai Lu , Dave Hansen , Andi Kleen Subject: Re: [PATCH] x86, mm: Reserver some memory for bootmem allocator for NO_BOOTMEM Message-ID: <20180831061519.3zbxsjs4rd6mmsuo@shbuild888> References: <20180830090319.985-1-feng.tang@intel.com> <20180830104401.GZ24124@hirez.programming.kicks-ass.net> <20180830111207.GE2656@dhcp22.suse.cz> <20180830124915.GH2656@dhcp22.suse.cz> <20180830125909.uq3e76akcmep6j2u@shbuild888> <20180830131920.w2jqjvlkpfb4ejb2@shbuild888> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2018 at 03:25:42PM +0200, Thomas Gleixner wrote: > And where is the problem? We know that we need the fixmap during early boot > anyway, so allocating the PTE page statically and setting it up early > enough is not really rocket science. No allocator required. Further check shows the page table for fixmap is already setup in [-12M, -10M], but fixmap's address space breaks the expection under certain kernel config. So here is another fix, please review, thanks! ---------------------------------------------------------------- >From f63e4e5c6166a2f8d13ad3142b7a49b2fd1f8edf Mon Sep 17 00:00:00 2001 From: Feng Tang Date: Fri, 31 Aug 2018 13:48:21 +0800 Subject: [PATCH] x86, mm: Make the real fixmap address consistent We hit a kernel panic when enabling earlycon for a platform, the call trace is: panic+0xd2/0x220 __alloc_bootmem+0x31/0x34 spp_getpage+0x60/0x8a fill_pte+0x71/0x130 __set_pte_vaddr+0x1d/0x50 set_pte_vaddr+0x3c/0x60 __native_set_fixmap+0x23/0x30 native_set_fixmap+0x30/0x40 setup_earlycon+0x1e0/0x32f param_setup_earlycon+0x13/0x22 do_early_param+0x5b/0x90 parse_args+0x1f7/0x300 parse_early_options+0x24/0x28 parse_early_param+0x65/0x73 setup_arch+0x31e/0x9f1 start_kernel+0x58/0x44e This panic happens as the earlycon's fixmap address has no pmd/pte ready, and __set_fixmap will try to allocate memory to setup the page table, and trigger panic due to no memory. x86 kernel actually prepares the page table for fixmap in head_64.S: NEXT_PAGE(level2_fixmap_pgt) .fill 506,8,0 .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ .fill 5,8,0 and it expects the fixmap address is in [-12M, -10M] range, but current code in fixmap.h will break the expectation when X86_VSYSCALL_EMULATION=n #ifdef CONFIG_X86_VSYSCALL_EMULATION VSYSCALL_PAGE = (FIXADDR_TOP - VSYSCALL_ADDR) >> PAGE_SHIFT, #endif So removing the "#ifdef" will make the fixmap address space stable in [-12M, -10M] and fix the issue. Signed-off-by: Feng Tang --- arch/x86/include/asm/fixmap.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h index e203169931c7..fcf27171f493 100644 --- a/arch/x86/include/asm/fixmap.h +++ b/arch/x86/include/asm/fixmap.h @@ -67,9 +67,7 @@ enum fixed_addresses { #ifdef CONFIG_X86_32 FIX_HOLE, #else -#ifdef CONFIG_X86_VSYSCALL_EMULATION VSYSCALL_PAGE = (FIXADDR_TOP - VSYSCALL_ADDR) >> PAGE_SHIFT, -#endif #endif FIX_DBGP_BASE, FIX_EARLYCON_MEM_BASE, -- 2.14.1