From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx206.postini.com [74.125.245.206]) by kanga.kvack.org (Postfix) with SMTP id 50D9C6B005A for ; Mon, 7 Jan 2013 16:53:46 -0500 (EST) Date: Mon, 7 Jan 2013 13:53:44 -0800 From: Andrew Morton Subject: Re: [PATCH 0/2] pageattr fixes for pmd/pte_present Message-Id: <20130107135344.5ca426ca.akpm@linux-foundation.org> In-Reply-To: <1357441197.9001.6.camel@kernel.cn.ibm.com> References: <1355767224-13298-1-git-send-email-aarcange@redhat.com> <1357441197.9001.6.camel@kernel.cn.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Simon Jeons Cc: Andrea Arcangeli , linux-mm@kvack.org, Andi Kleen , Shaohua Li , "H. Peter Anvin" , Mel Gorman , Hugh Dickins On Sat, 05 Jan 2013 20:59:57 -0600 Simon Jeons wrote: > (top-posting repaired) top-posting makes it really hard to reply to your email in a useful fashion. So if you want a reply, please don't top-post! > On Mon, 2012-12-17 at 19:00 +0100, Andrea Arcangeli wrote: > > Hi, > > > > I got a report for a minor regression introduced by commit > > 027ef6c87853b0a9df53175063028edb4950d476. > > > > So the problem is, pageattr creates kernel pagetables (pte and pmds) > > that breaks pte_present/pmd_present and the patch above exposed this > > invariant breakage for pmd_present. > > > > The same problem already existed for the pte and pte_present and it > > was fixed by commit 660a293ea9be709b893d371fbc0328fcca33c33a (if it > > wasn't for that commit, it wouldn't even be a regression). That fix > > avoids the pagefault to use pte_present. I could follow through by > > stopping using pmd_present/pmd_huge too. > > > > However I think it's more robust to fix pageattr and to clear the > > PSE/GLOBAL bitflags too in addition to the present bitflag. So the > > kernel page fault can keep using the regular > > pte_present/pmd_present/pmd_huge. > > > > The confusion arises because _PAGE_GLOBAL and _PAGE_PROTNONE are > > sharing the same bit, and in the pmd case we pretend _PAGE_PSE to be > > set only in present pmds (to facilitate split_huge_page final tlb > > flush). > > > > What's the status of these two patches? I expect they fell through the christmas cracks. I added them to my (getting large) queue of x86 patches for consideration by the x86 maintainers. Why do you ask? It seems the bug is a pretty minor one and that we need only fix it in 3.8 or even 3.9. Is that supposition incorrect? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org