From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: xen@randonwebstuff.com, Laura Abbott <labbott@redhat.com>,
linux-mm@kvack.org, bugzilla-daemon@bugzilla.kernel.org
Subject: Re: [Bug 198497] New: handle_mm_fault / xen_pmd_val / radix_tree_lookup_slot Null pointer
Date: Thu, 12 Apr 2018 10:28:32 -0700 [thread overview]
Message-ID: <20180412172832.GC24728@bombadil.infradead.org> (raw)
In-Reply-To: <20180412101209.311c5ee1759449877b233183@linux-foundation.org>
On Thu, Apr 12, 2018 at 10:12:09AM -0700, Andrew Morton wrote:
> On Fri, 9 Feb 2018 06:47:26 -0800 Matthew Wilcox <willy@infradead.org> wrote:
>
> >
> > ping?
> >
>
> There have been a bunch of updates to this issue in bugzilla
> (https://bugzilla.kernel.org/show_bug.cgi?id=198497). Sigh, I don't
> know what to do about this - maybe there's some way of getting bugzilla
> to echo everything to linux-mm or something.
>
> Anyway, please take a look - we appear to have a bug here. Perhaps
> this bug is sufficiently gnarly for you to prepare a debugging patch
> which we can add to the mainline kernel so we get (much) more debugging
> info when people hit it?
I have a few thoughts ...
- The debugging patch I prepared appears to be doing its job well.
People get the message and their machine stays working.
- The commonality appears to be Xen running 32-bit kernels. Maybe we
can kick the problem over to them to solve?
- If we are seeing corruption purely in the lower bits, *we'll never
know*. The radix tree lookup will simply not find anything, and all
will be well. That said, the bad PTE values reported in that bug have
the NX bit and one other bit set; generally bit 32, 33 or 34. I have
an idea for adding a parity bit, but haven't had time to implement it.
Anyone have an intern who wants an interesting kernel project to work on?
Given that this is happening on Xen, I wonder if Xen is using some of the
bits in the page table for its own purposes.
next prev parent reply other threads:[~2018-04-12 17:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-198497-27@https.bugzilla.kernel.org/>
2018-01-18 21:55 ` [Bug 198497] New: handle_mm_fault / xen_pmd_val / radix_tree_lookup_slot Null pointer Andrew Morton
2018-01-18 22:18 ` Laura Abbott
2018-01-19 3:04 ` Matthew Wilcox
2018-01-19 3:14 ` xen
2018-01-19 13:21 ` Matthew Wilcox
2018-01-19 17:30 ` Laura Abbott
2018-01-26 6:54 ` xen
2018-01-26 19:40 ` Matthew Wilcox
2018-01-29 22:26 ` xen
2018-01-31 10:54 ` Matthew Wilcox
2018-01-31 23:02 ` Tetsuo Handa
2018-02-01 9:48 ` Matthew Wilcox
2018-02-09 14:47 ` Matthew Wilcox
2018-04-12 17:12 ` Andrew Morton
2018-04-12 17:28 ` Matthew Wilcox [this message]
2018-01-19 13:33 ` Matthew Wilcox
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