From: Andrew Morton <akpm@linux-foundation.org>
To: Simon Jeons <simon.jeons@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, Andi Kleen <andi@firstfloor.org>,
Shaohua Li <shaohua.li@intel.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH 0/2] pageattr fixes for pmd/pte_present
Date: Mon, 7 Jan 2013 13:53:44 -0800 [thread overview]
Message-ID: <20130107135344.5ca426ca.akpm@linux-foundation.org> (raw)
In-Reply-To: <1357441197.9001.6.camel@kernel.cn.ibm.com>
On Sat, 05 Jan 2013 20:59:57 -0600
Simon Jeons <simon.jeons@gmail.com> 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?
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next prev parent reply other threads:[~2013-01-07 21:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-17 18:00 [PATCH 0/2] pageattr fixes for pmd/pte_present Andrea Arcangeli
2012-12-17 18:00 ` [PATCH 1/2] Revert "x86, mm: Make spurious_fault check explicitly check the PRESENT bit" Andrea Arcangeli
2012-12-17 18:17 ` H. Peter Anvin
2012-12-17 18:35 ` Andrea Arcangeli
2012-12-17 18:00 ` [PATCH 2/2] pageattr: prevent PSE and GLOABL leftovers to confuse pmd/pte_present and pmd_huge Andrea Arcangeli
2013-01-10 7:59 ` Simon Jeons
2013-01-06 2:59 ` [PATCH 0/2] pageattr fixes for pmd/pte_present Simon Jeons
2013-01-07 21:53 ` Andrew Morton [this message]
2013-01-07 21:55 ` H. Peter Anvin
2013-01-08 12:25 ` Andrea Arcangeli
2013-01-10 7:42 ` Simon Jeons
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