From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753927AbcGVK1Z (ORCPT ); Fri, 22 Jul 2016 06:27:25 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47972 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753298AbcGVK1U (ORCPT ); Fri, 22 Jul 2016 06:27:20 -0400 Date: Fri, 22 Jul 2016 03:26:04 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: toshi.kani@hp.com, linux-kernel@vger.kernel.org, mario_limonciello@dell.com, bp@alien8.de, jpoimboe@redhat.com, dvlasenk@redhat.com, akpm@linux-foundation.org, mcgrof@suse.com, brgerst@gmail.com, torvalds@linux-foundation.org, mingo@kernel.org, hpa@zytor.com, tglx@linutronix.de, mjg59@srcf.ucam.org, luto@kernel.org, peterz@infradead.org, keescook@chromium.org Reply-To: dvlasenk@redhat.com, jpoimboe@redhat.com, akpm@linux-foundation.org, bp@alien8.de, linux-kernel@vger.kernel.org, toshi.kani@hp.com, mario_limonciello@dell.com, tglx@linutronix.de, brgerst@gmail.com, mcgrof@suse.com, torvalds@linux-foundation.org, mingo@kernel.org, hpa@zytor.com, keescook@chromium.org, peterz@infradead.org, mjg59@srcf.ucam.org, luto@kernel.org In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/boot] x86/boot: Simplify EBDA-vs-BIOS reservation logic Git-Commit-ID: 6a79296cb15d947bcb4558011fe066e5d8252b35 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 6a79296cb15d947bcb4558011fe066e5d8252b35 Gitweb: http://git.kernel.org/tip/6a79296cb15d947bcb4558011fe066e5d8252b35 Author: Andy Lutomirski AuthorDate: Thu, 21 Jul 2016 14:16:52 -0700 Committer: Ingo Molnar CommitDate: Fri, 22 Jul 2016 11:46:01 +0200 x86/boot: Simplify EBDA-vs-BIOS reservation logic Both the intent and the effect of reserve_bios_regions() is simple: reserve the range from the apparent BIOS start (suitably filtered) through 1MB and, if the EBDA start address is sensible, extend that reservation downward to cover the EBDA as well. The code is overcomplicated, though, and contains head-scratchers like: if (ebda_start < BIOS_START_MIN) ebda_start = BIOS_START_MAX; That snipped is trying to say "if ebda_start < BIOS_START_MIN, ignore it". Simplify it: reorder the code so that it makes sense. This should have no functional effect under any circumstances. Signed-off-by: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Kees Cook Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Mario Limonciello Cc: Matthew Garrett Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Link: http://lkml.kernel.org/r/ef89c0c761be20ead8bd9a3275743e6259b6092a.1469135598.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/ebda.c | 34 +++++++++++----------------------- 1 file changed, 11 insertions(+), 23 deletions(-) diff --git a/arch/x86/kernel/ebda.c b/arch/x86/kernel/ebda.c index 6219eef..4312f8a 100644 --- a/arch/x86/kernel/ebda.c +++ b/arch/x86/kernel/ebda.c @@ -65,22 +65,6 @@ void __init reserve_bios_regions(void) if (!x86_platform.legacy.reserve_bios_regions) return; - /* Get the start address of the EBDA page: */ - ebda_start = get_bios_ebda(); - - /* - * Quirk: some old Dells seem to have a 4k EBDA without - * reporting so in their BIOS RAM size value, so just - * consider the memory above 640K to be off limits - * (bugzilla 2990). - * - * We detect this case by filtering for nonsensical EBDA - * addresses below 128K, where we can assume that they - * are bogus and bump it up to a fixed 640K value: - */ - if (ebda_start < BIOS_START_MIN) - ebda_start = BIOS_START_MAX; - /* * BIOS RAM size is encoded in kilobytes, convert it * to bytes to get a first guess at where the BIOS @@ -91,18 +75,22 @@ void __init reserve_bios_regions(void) /* * If bios_start is less than 128K, assume it is bogus - * and bump it up to 640K: + * and bump it up to 640K. Similarly, if bios_start is above 640K, + * don't trust it. */ - if (bios_start < BIOS_START_MIN) + if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX) bios_start = BIOS_START_MAX; + /* Get the start address of the EBDA page: */ + ebda_start = get_bios_ebda(); + /* - * Use the lower of the bios_start and ebda_start - * as the starting point, but don't allow it to - * go beyond 640K: + * If the EBDA start address is sane and is below the BIOS region, + * then also reserve everything from the EBDA start address up to + * the BIOS region. */ - bios_start = min(bios_start, ebda_start); - bios_start = min(bios_start, BIOS_START_MAX); + if (ebda_start >= BIOS_START_MIN && ebda_start < bios_start) + bios_start = ebda_start; /* Reserve all memory between bios_start and the 1MB mark: */ memblock_reserve(bios_start, 0x100000 - bios_start);