Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)

From	Dan Williams <dan.j.williams@intel.com>
Newsgroups	linux.kernel
Subject	Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)
Date	2016-09-09 17:50 +0200
Message-ID	<sfwdY-4Pt-19@gated-at.bofh.it> (permalink)
References	<seZi1-15I-15@gated-at.bofh.it> <sfgsz-3pz-85@gated-at.bofh.it> <sfgCd-3HW-23@gated-at.bofh.it> <sfpYR-VU-19@gated-at.bofh.it>
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On Fri, Sep 9, 2016 at 1:55 AM, Xiao Guangrong
<guangrong.xiao@linux.intel.com> wrote:
[..]
>>
>> Whether a persistent memory mapping requires an msync/fsync is a
>> filesystem specific question.  This mincore proposal is separate from
>> that.  Consider device-DAX for volatile memory or mincore() called on
>> an anonymous memory range.  In those cases persistence and filesystem
>> metadata are not in the picture, but it would still be useful for
>> userspace to know "is there page cache backing this mapping?" or "what
>> is the TLB geometry of this mapping?".
>
>
> I got a question about msync/fsync which is beyond the topic of this thread
> :)
>
> Whether msync/fsync can make data persistent depends on ADR feature on
> memory
> controller, if it exists everything works well, otherwise, we need to have
> another
> interface that is why 'Flush hint table' in ACPI comes in. 'Flush hint
> table' is
> particularly useful for nvdimm virtualization if we use normal memory to
> emulate
> nvdimm with data persistent characteristic (the data will be flushed to a
> persistent storage, e.g, disk).
>
> Does current PMEM programming model fully supports 'Flush hint table'? Is
> userspace allowed to use these addresses?

If you publish flush hint addresses in the virtual NFIT the guest VM
will write to them whenever a REQ_FLUSH or REQ_FUA request is sent to
the virtual /dev/pmemX device.  Yes, seems straightforward to take a
VM exit on those events and flush simulated pmem to persistent
storage.

Thread

DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams <dan.j.williams@intel.com> - 2016-09-08 06:40 +0200
  Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-09-09 01:00 +0200
    Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams <dan.j.williams@intel.com> - 2016-09-09 01:10 +0200
      Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-09-09 11:10 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams <dan.j.williams@intel.com> - 2016-09-09 17:50 +0200
          Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-09-12 08:10 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) "Rudoff, Andy" <andy.rudoff@intel.com> - 2016-09-12 05:50 +0200
          Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-09-12 08:40 +0200
    Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-12 03:50 +0200
      Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-09-15 08:00 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-15 08:30 +0200
    Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 07:30 +0200
      Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) "Oliver O'Halloran" <oohall@gmail.com> - 2016-09-12 09:30 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 10:00 +0200
          Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-12 10:10 +0200
            Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 17:10 +0200
              Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 03:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams <dan.j.williams@intel.com> - 2016-09-13 06:10 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 07:50 +0200
            Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-12 23:40 +0200
              Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 04:00 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-13 09:20 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 11:10 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-14 09:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-14 12:20 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-15 04:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-15 06:00 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-15 12:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-15 13:50 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-16 00:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-16 08:00 +0200

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