From patchwork Mon Oct 5 14:05:26 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tim Gardner X-Patchwork-Id: 526342 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 28CBA14090A; Tue, 6 Oct 2015 01:06:42 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1Zj6PX-0001vb-1A; Mon, 05 Oct 2015 14:06:39 +0000 Received: from mail-pa0-f43.google.com ([209.85.220.43]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1Zj6P8-0001hw-6K for kernel-team@lists.ubuntu.com; Mon, 05 Oct 2015 14:06:14 +0000 Received: by padhy16 with SMTP id hy16so38044420pad.1 for ; Mon, 05 Oct 2015 07:06:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references; bh=ZCFNwTPbpz/iv/3UtzLkTXVtu7rHc+5uXrzXlq8fU3I=; b=bhUJtrXKzQjmOCzgz9CwHfEr7EG9QIJ95MH5OeMAjShBcxoou6FxoXNOyK+Abvfzjj Pwo90Ig4KMRcVRoItSxrfk3kuzDb8aEKtwrVC7IXnMB59A+DXg/zzrY2SvIJfFo++mcd GIL3OU4xP/rrghYZYsVG9stLshlmfMlMIhcgZGZKm7JlUmWPTLPX2pit/fYDGQGzc/KB ly3tYyXOpCTGxH+CZltEhYbyrQgPCAeqBFQ8yrIgYT5s267w++pqruN3e46mxNY65MOR 9HFFEK17i+SWCszho7q7gBJql+g/YvPFKwwbE2z5SWO2CBVQCSAUoMuG1C948zqrGFC2 h3wQ== X-Gm-Message-State: ALoCoQmriE1PAWLx5XlJqe+rnboe8kRc0GeEAYLVQHjZFHsiWHwYyq7GQUR7MgNBnTM0y6tuUva5 X-Received: by 10.68.190.5 with SMTP id gm5mr40249951pbc.25.1444053973564; Mon, 05 Oct 2015 07:06:13 -0700 (PDT) Received: from localhost.localdomain (host-174-45-38-91.hln-mt.client.bresnan.net. [174.45.38.91]) by smtp.gmail.com with ESMTPSA id rp5sm28100596pab.0.2015.10.05.07.06.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 05 Oct 2015 07:06:12 -0700 (PDT) From: tim.gardner@canonical.com To: kernel-team@lists.ubuntu.com Subject: [PATCH 22/22] x86/vm86: Fix the misleading CONFIG_VM86 Kconfig help text Date: Mon, 5 Oct 2015 08:05:26 -0600 Message-Id: <1444053926-18032-23-git-send-email-tim.gardner@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1444053926-18032-1-git-send-email-tim.gardner@canonical.com> References: <1444053926-18032-1-git-send-email-tim.gardner@canonical.com> X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com From: Ingo Molnar BugLink: http://bugs.launchpad.net/bugs/1499089 The CONFIG_VM86 Kconfig help text is actively misleading, so fix it: - Don't mark it 'obsolete' in the text as we'll support the ABI as long as CPUs support it. - Qualify the part about software emulation and mention that for some apps you want a real vm86 mode. - Don't scare users away from the option, instead explain what it does. Reported-by: Stas Sergeev Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Austin S Hemmelgarn Cc: Borislav Petkov Cc: Brian Gerst Cc: Josh Boyer Cc: Kees Cook Cc: Linus Torvalds Cc: Matthew Garrett Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar (cherry picked from commit 1e6428124fe22906be0de1622c8fed8e50e5de05) Signed-off-by: Tim Gardner --- arch/x86/Kconfig | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a6529c1..ac2d50c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1003,7 +1003,7 @@ config X86_THERMAL_VECTOR depends on X86_MCE_INTEL config X86_LEGACY_VM86 - bool "Legacy VM86 support (obsolete)" + bool "Legacy VM86 support" default n depends on X86_32 ---help--- @@ -1015,19 +1015,20 @@ config X86_LEGACY_VM86 available to accelerate real mode DOS programs. However, any recent version of DOSEMU, X, or vbetool should be fully functional even without kernel VM86 support, as they will all - fall back to (pretty well performing) software emulation. + fall back to software emulation. Nevertheless, if you are using + a 16-bit DOS program where 16-bit performance matters, vm86 + mode might be faster than emulation and you might want to + enable this option. - Anything that works on a 64-bit kernel is unlikely to need - this option, as 64-bit kernels don't, and can't, support V8086 - mode. This option is also unrelated to 16-bit protected mode - and is not needed to run most 16-bit programs under Wine. + Note that any app that works on a 64-bit kernel is unlikely to + need this option, as 64-bit kernels don't, and can't, support + V8086 mode. This option is also unrelated to 16-bit protected + mode and is not needed to run most 16-bit programs under Wine. - Enabling this option adds considerable attack surface to the - kernel and slows down system calls and exception handling. + Enabling this option increases the complexity of the kernel + and slows down exception handling a tiny bit. - Unless you use very old userspace or need the last drop of - performance in your real mode DOS games and can't use KVM, - say N here. + If unsure, say N here. config VM86 bool