Re: [PATCH] x86: fix kaslr and memmap collision

From	Dave Chinner <david@fromorbit.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86: fix kaslr and memmap collision
Date	2016-11-24 01:10 +0100
Message-ID	<sGPLX-3nP-11@gated-at.bofh.it> (permalink)
References	<sG78d-8kM-3@gated-at.bofh.it> <sGeW5-4Pc-15@gated-at.bofh.it> <sGnd0-1Py-13@gated-at.bofh.it> <sGosq-2Ad-19@gated-at.bofh.it> <sGoC5-2SE-19@gated-at.bofh.it>
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On Tue, Nov 22, 2016 at 11:01:32AM -0800, Dan Williams wrote:
> On Tue, Nov 22, 2016 at 10:54 AM, Kees Cook <keescook@chromium.org> wrote:
> > On Tue, Nov 22, 2016 at 9:26 AM, Dan Williams <dan.j.williams@intel.com> wrote:
> >> No, you're right, we need to handle multiple ranges.  Since the
> >> mem_avoid array is statically allocated perhaps we can handle up to 4
> >> memmap= entries, but past that point disable kaslr for that boot?
> >
> > Yeah, that seems fine to me. I assume it's rare to have 4?
> >
> 
> It should be rare to have *one* since ACPI 6.0 added support for
> communicating persistent memory ranges.  However there are legacy
> nvdimm users that I know are doing at least 2, but I have hard time
> imagining they would ever do more than 4.

I doubt it's rare amongst the people using RAM to emulate pmem for
filesystem testing purposes. My "pmem" test VM always has at least 2
ranges set to give me two discrete pmem devices, and I have used 4
from time to time to do things like test multi-volume scratch XFS
filesystems in xfstests (i.e. data, log and realtime volumes) so I
didn't need to play games with partitioning or DM...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Thread

[PATCH] x86: fix kaslr and memmap collision Dave Jiang <dave.jiang@intel.com> - 2016-11-22 01:30 +0100
  Re: [PATCH] x86: fix kaslr and memmap collision Ingo Molnar <mingo@kernel.org> - 2016-11-22 09:50 +0100
    Re: [PATCH] x86: fix kaslr and memmap collision Dan Williams <dan.j.williams@intel.com> - 2016-11-22 18:40 +0100
      Re: [PATCH] x86: fix kaslr and memmap collision Kees Cook <keescook@chromium.org> - 2016-11-22 20:00 +0100
        Re: [PATCH] x86: fix kaslr and memmap collision Dan Williams <dan.j.williams@intel.com> - 2016-11-22 20:10 +0100
          Re: [PATCH] x86: fix kaslr and memmap collision Kees Cook <keescook@chromium.org> - 2016-11-22 23:40 +0100
          Re: [PATCH] x86: fix kaslr and memmap collision Dave Chinner <david@fromorbit.com> - 2016-11-24 01:10 +0100
            Re: [PATCH] x86: fix kaslr and memmap collision Dan Williams <dan.j.williams@intel.com> - 2016-11-24 20:40 +0100

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