From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH] VMI: remove CONFIG_DEBUG_PAGE_TYPE and associated bitrotted code Date: Fri, 06 Jul 2007 13:34:21 -0700 Message-ID: <468EA74D.7010706@vmware.com> References: <468E890A.1070504@s5r6.in-berlin.de> <20070706201625.GT4306@sequoia.sous-sol.org> <468EA27C.9060401@vmware.com> <468EA5E0.4070501@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <468EA5E0.4070501@goop.org> Sender: linux-kernel-owner@vger.kernel.org To: Jeremy Fitzhardinge Cc: Chris Wright , Andrew Morton , Linux Kernel Mailing List , virtualization@lists.osdl.org, Stefan Richter , "Robert P. J. Day" List-Id: virtualization@lists.linuxfoundation.org Jeremy Fitzhardinge wrote: >> >> I never merged the whole bit upstream because it added a field to >> struct page. > > Hm, is that a big problem? It would be OK for a debug config option, > wouldn't it? Also, it doesn't seem particularly vmi-specific. Could > it be made part of the pvops infrastructure? I though about it, but it gets really ugly. You need wrappers for all the MMU ops in pvops generic code, which means either another layer of wrappers or a bunch of CONFIG_DEBUG_PARAVIRT only things that are easy to break because they also depend on PAE vs. non-PAE. It's doable, though, and might even be extensible to s390 for CMM page type debugging, as well as descriptor type tracking and enforcement of page isolation of GDTs. Page state tracking could track - PAGE_ZERO, PAGE_UNUSED, PAGE_STABLE, PAGE_VOLATILE, PAGE_POTENTIALLY_VOLATILE, PAGE_L1{2/3/4}, PAGE_LDT, PAGE_GDT, actually, no this seems silly, since we'd just be duplicating bits for the page types, so the only debug benefit is ensuring the intersection of volatile and L{1/2/3/4} is nil, which is already trivially verifiable by inspection. Zach