From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: kvm-88: KVM_APIC_READ: read reserved register b0 Date: Sun, 30 Aug 2009 14:49:59 +0300 Message-ID: <20090830114959.GV30093@redhat.com> References: <4A97AB92.9090509@l-mx.de> <20090829212036.GA3014@defiant.freesoftware.org> <4A9A4D7F.3010904@l-mx.de> <20090830100159.GT30093@redhat.com> <4A9A6596.3010302@l-mx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dbareiro@gmx.net, kvm@vger.kernel.org To: Christoph Lechner Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59340 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753332AbZH3LuL (ORCPT ); Sun, 30 Aug 2009 07:50:11 -0400 Content-Disposition: inline In-Reply-To: <4A9A6596.3010302@l-mx.de> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Aug 30, 2009 at 01:42:14PM +0200, Christoph Lechner wrote: > Gleb Natapov wrote: > > This printk no longer exists in upstream kvm. > > > > just to be curious: What was the reason to add that debugging message? > Because well behaved OS shouldn't read write only register. Unfortunately older Linux kernels sometimes uses xchg to access eoi(b0) apic register which will generate read/write. > I don't know much about the background of the message, but I assume that > it is useful. So wouldn't it be a idea to keep the code for the message > where it is and just throttle the rate it is reported? > It's not too much useful unless you are debugging a guest. -- Gleb.