From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752171AbaHTP0M (ORCPT ); Wed, 20 Aug 2014 11:26:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43616 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751829AbaHTP0H (ORCPT ); Wed, 20 Aug 2014 11:26:07 -0400 From: Frantisek Hrbata To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, oleg@redhat.com, kamaleshb@in.ibm.com, hechjie@cn.ibm.com, akpm@linux-foundation.org, dave.hansen@intel.com, dvlasenk@redhat.com, prarit@redhat.com, lwoodman@redhat.com, hannsj_uhl@de.ibm.com Subject: [PATCH 0/2] x86: allow read/write /dev/mem to access non-system RAM above high_memory Date: Wed, 20 Aug 2014 17:25:24 +0200 Message-Id: <1408548326-18665-1-git-send-email-fhrbata@redhat.com> In-Reply-To: <1408103043-31015-1-git-send-email-fhrbata@redhat.com> References: <1408103043-31015-1-git-send-email-fhrbata@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, this patch set depends on the following patches posted earlier. [PATCH V2 1/2] x86: add arch_pfn_possible helper lkml: Message-Id: <1408103043-31015-2-git-send-email-fhrbata@redhat.com> [PATCH V2 2/2] x86: add phys addr validity check for /dev/mem mmap lkml: Message-Id: <1408103043-31015-3-git-send-email-fhrbata@redhat.com> This is an attempt to remove the high_memory limit for the read/write access to /dev/mem. IMHO there is no reason for this limit on x86. It is presented in the generic valid_phys_addr_range, which is used only by (read|write)_mem. IIUIC it's main purpose is for the generic xlate_dev_mem_ptr, which is using only the direct kernel mapping __va translation. Since the valid_phys_addr_range is called as the first check in (read|write)_mem, it basically does not allow to access anything above high_memory on x86. The first patch adds high_memory check to x86's (xlate|unxlate)_dev_mem_ptr, so the direct kernel mapping can be safely used for system RAM bellow high_memory. This is IMHO the only valid reason to use high_memory check in (read|write)_mem. The second patch removes the high_memory check from valid_phys_addr_range, allowing read/write to access non-system RAM above high_memory. So far this was possible only by using mmap. I hope I haven't overlooked something. Many thanks Frantisek Hrbata (2): x86: add high_memory check to (xlate|unxlate)_dev_mem_ptr x86: remove high_memory check from valid_phys_addr_range arch/x86/mm/ioremap.c | 9 ++++++--- arch/x86/mm/mmap.c | 2 +- 2 files changed, 7 insertions(+), 4 deletions(-) -- 1.9.3