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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BE6BC4332F for ; Thu, 17 Mar 2022 19:03:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235842AbiCQTE2 (ORCPT ); Thu, 17 Mar 2022 15:04:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237814AbiCQTE1 (ORCPT ); Thu, 17 Mar 2022 15:04:27 -0400 Received: from srv1.home.kabele.me (unknown [IPv6:2a02:768:2704:8c1a:3eec:efff:fe00:2ce4]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4CBC6BD7CA; Thu, 17 Mar 2022 12:03:05 -0700 (PDT) Received: from srv1.home.kabele.me (localhost [IPv6:::1]) by srv1.home.kabele.me (Postfix) with ESMTP id C6C421692B3; Thu, 17 Mar 2022 20:03:08 +0100 (CET) Received: from localhost ([2a01:c22:8dfa:1400:beea:2810:7764:7afc]) by srv1.home.kabele.me with ESMTPSA id CG36LOyFM2ITWTQAnmUwTQ (envelope-from ); Thu, 17 Mar 2022 20:03:08 +0100 Date: Thu, 17 Mar 2022 20:03:03 +0100 From: Vit Kabele To: platform-driver-x86@vger.kernel.org Cc: r.marek@assembler.cz, devel@acpica.org, mingo@redhat.com, robert.moore@intel.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: [PATCH 3/3 RESEND] acpica: Do not touch VGA memory when EBDA < 1KiB Message-ID: Mail-Followup-To: platform-driver-x86@vger.kernel.org, r.marek@assembler.cz, devel@acpica.org, mingo@redhat.com, robert.moore@intel.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org The ACPICA code assumes that EBDA region must be at least 1KiB in size. Because this is not guaranteed, it might happen that while scanning the memory for RSDP pointer, the kernel touches memory above 640KiB. This is unwanted as the VGA memory range may not be decoded or even present when running under virtualization. Signed-off-by: Vit Kabele Reviewed-by: Rudolf Marek --- drivers/acpi/acpica/tbxfroot.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/drivers/acpi/acpica/tbxfroot.c b/drivers/acpi/acpica/tbxfroot.c index 67b7df1c0520..b1f4a91044d9 100644 --- a/drivers/acpi/acpica/tbxfroot.c +++ b/drivers/acpi/acpica/tbxfroot.c @@ -114,6 +114,7 @@ acpi_find_root_pointer(acpi_physical_address *table_address) u8 *table_ptr; u8 *mem_rover; u32 physical_address; + u32 ebda_window_size; ACPI_FUNCTION_TRACE(acpi_find_root_pointer); @@ -143,25 +144,32 @@ acpi_find_root_pointer(acpi_physical_address *table_address) */ if (physical_address > 0x400 && physical_address < 0xA0000) { + /* Calculate the scan window size + * The EBDA is not guaranteed to be larger than a KiB + * and in case that it is smaller the scanning function would + * leave the low memory and continue to the VGA range. + */ + ebda_window_size = ACPI_MIN(ACPI_EBDA_WINDOW_SIZE, + 0xA0000 - physical_address); + /* - * 1b) Search EBDA paragraphs (EBDA is required to be a - * minimum of 1K length) + * 1b) Search EBDA paragraphs */ table_ptr = acpi_os_map_memory((acpi_physical_address) physical_address, - ACPI_EBDA_WINDOW_SIZE); + ebda_window_size); if (!table_ptr) { ACPI_ERROR((AE_INFO, "Could not map memory at 0x%8.8X for length %u", - physical_address, ACPI_EBDA_WINDOW_SIZE)); + physical_address, ebda_window_size)); return_ACPI_STATUS(AE_NO_MEMORY); } mem_rover = acpi_tb_scan_memory_for_rsdp(table_ptr, - ACPI_EBDA_WINDOW_SIZE); - acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE); + ebda_window_size); + acpi_os_unmap_memory(table_ptr, ebda_window_size); if (mem_rover) { -- 2.30.2