Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763858AbZLQBvY (ORCPT ); Wed, 16 Dec 2009 20:51:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936149AbZLQBvO (ORCPT ); Wed, 16 Dec 2009 20:51:14 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:47987 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763779AbZLQBu5 (ORCPT ); Wed, 16 Dec 2009 20:50:57 -0500 Subject: Re: [RFC][Patch] IBM Real-Time "SMI Free" mode drive -v2 From: Keith Mannthey To: Peter Zijlstra Cc: lkml , John Stultz In-Reply-To: <1261004964.21028.521.camel@laptop> References: <1260907788.6521.10.camel@keith-laptop> <1261004964.21028.521.camel@laptop> Content-Type: text/plain Date: Wed, 16 Dec 2009 17:50:55 -0800 Message-Id: <1261014655.6521.84.camel@keith-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2074 Lines: 50 On Thu, 2009-12-17 at 00:09 +0100, Peter Zijlstra wrote: > On Tue, 2009-12-15 at 12:09 -0800, Keith Mannthey wrote: > > This driver supports the Real-Time Linux (RTL) BIOS feature. The RTL > > feature allows non-fatal System Management Interrupts (SMIs) to be > > disabled on supported IBM platforms. > > > > > > The Device is presented as a special "_rtl_" table to the OS in the > > Extended BIOS Data Area. There is a simple protocol for entering and > > exiting the mode at runtime. This driver creates a simple sysfs > > interface to allow a simple entry and exit from RTL mode in the > > UFI/BIOS. > > Why not simply always run with these non-fatal SMIs disabled and provide > their function through the OS proper? > > That way you don't need no silly switches and gain consistent platform > behaviour. Peter, This driver will load and work on widely used Intel and AMD based IBM hardware. A decent amount of the IBM blades and a few of the rack-mount servers with regular firmware support this mode. This is not special hardware with special features is is regular hardware/firmware that can enter this special mode. There are 2 major things that change when you in this mode that keep it from being a good fit for many situations. 1. ECC memory error detection and reporting is the sole responsibility of the OS. I have practical experience with this and let just say this does not "just work" everywhere even within Linux. 2. The cpu can no longer be externally throttled. This means externally implemented cooling or power saving options just don't work. These 2 things make it impractical for it to be an all the time everywhere type of thing. I think a run time state change the OS can request is a good fit for the issues and complications at hand. Thanks, Keith Mannthey LTC Real-Time -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/