<feed xmlns='http://www.w3.org/2005/Atom'>
<title>kernel/linux.git/arch/x86/include/asm/cacheflush.h, branch v6.12.80</title>
<subtitle>Linux kernel stable tree (mirror)</subtitle>
<id>https://git.radix-linux.su/kernel/linux.git/atom?h=v6.12.80</id>
<link rel='self' href='https://git.radix-linux.su/kernel/linux.git/atom?h=v6.12.80'/>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/'/>
<updated>2020-06-08T18:05:57+00:00</updated>
<entry>
<title>asm-generic: don't include &lt;linux/mm.h&gt; in cacheflush.h</title>
<updated>2020-06-08T18:05:57+00:00</updated>
<author>
<name>Christoph Hellwig</name>
<email>hch@lst.de</email>
</author>
<published>2020-06-08T04:41:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=e0cf615d725cb3b69f0bdf1d8afdd4d4c31b4fd1'/>
<id>urn:sha1:e0cf615d725cb3b69f0bdf1d8afdd4d4c31b4fd1</id>
<content type='text'>
This seems to lead to some crazy include loops when using
asm-generic/cacheflush.h on more architectures, so leave it to the arch
header for now.

[hch@lst.de: fix warning]
  Link: http://lkml.kernel.org/r/20200520173520.GA11199@lst.de

Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Cc: Nick Piggin &lt;npiggin@gmail.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Jeff Dike &lt;jdike@addtoit.com&gt;
Cc: Richard Weinberger &lt;richard@nod.at&gt;
Cc: Anton Ivanov &lt;anton.ivanov@cambridgegreys.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: "H. Peter Anvin" &lt;hpa@zytor.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Vishal Verma &lt;vishal.l.verma@intel.com&gt;
Cc: Dave Jiang &lt;dave.jiang@intel.com&gt;
Cc: Keith Busch &lt;keith.busch@intel.com&gt;
Cc: Ira Weiny &lt;ira.weiny@intel.com&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Link: http://lkml.kernel.org/r/20200515143646.3857579-7-hch@lst.de
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>License cleanup: add SPDX GPL-2.0 license identifier to files with no license</title>
<updated>2017-11-02T10:10:55+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2017-11-01T14:07:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=b24413180f5600bcb3bb70fbed5cf186b60864bd'/>
<id>urn:sha1:b24413180f5600bcb3bb70fbed5cf186b60864bd</id>
<content type='text'>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode &amp; Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained &gt;5
   lines of source
 - File already had some variant of a license header in it (even if &lt;5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart &lt;kstewart@linuxfoundation.org&gt;
Reviewed-by: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>libnvdimm, nd_blk: remove mmio_flush_range()</title>
<updated>2017-08-31T22:05:10+00:00</updated>
<author>
<name>Robin Murphy</name>
<email>robin.murphy@arm.com</email>
</author>
<published>2017-08-31T11:27:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=5deb67f77a266010e2c10fb124b7516d0d258ce8'/>
<id>urn:sha1:5deb67f77a266010e2c10fb124b7516d0d258ce8</id>
<content type='text'>
mmio_flush_range() suffers from a lack of clearly-defined semantics,
and is somewhat ambiguous to port to other architectures where the
scope of the writeback implied by "flush" and ordering might matter,
but MMIO would tend to imply non-cacheable anyway. Per the rationale
in 67a3e8fe9015 ("nd_blk: change aperture mapping from WC to WB"), the
only existing use is actually to invalidate clean cache lines for
ARCH_MEMREMAP_PMEM type mappings *without* writeback. Since the recent
cleanup of the pmem API, that also now happens to be the exact purpose
of arch_invalidate_pmem(), which would be a far more well-defined tool
for the job.

Rather than risk potentially inconsistent implementations of
mmio_flush_range() for the sake of one callsite, streamline things by
removing it entirely and instead move the ARCH_MEMREMAP_PMEM related
definitions up to the libnvdimm level, so they can be shared by NFIT
as well. This allows NFIT to be enabled for arm64.

Signed-off-by: Robin Murphy &lt;robin.murphy@arm.com&gt;
Signed-off-by: Dan Williams &lt;dan.j.williams@intel.com&gt;
</content>
</entry>
<entry>
<title>treewide: decouple cacheflush.h and set_memory.h</title>
<updated>2017-05-09T00:15:14+00:00</updated>
<author>
<name>Laura Abbott</name>
<email>labbott@redhat.com</email>
</author>
<published>2017-05-08T22:58:47+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=e6ccbff0e90cf4bf012bf369dbdaf84c6faaedaa'/>
<id>urn:sha1:e6ccbff0e90cf4bf012bf369dbdaf84c6faaedaa</id>
<content type='text'>
Now that all call sites, completely decouple cacheflush.h and
set_memory.h

[sfr@canb.auug.org.au: kprobes/x86: merge fix for set_memory.h decoupling]
  Link: http://lkml.kernel.org/r/20170418180903.10300fd3@canb.auug.org.au
Link: http://lkml.kernel.org/r/1488920133-27229-17-git-send-email-labbott@redhat.com
Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Signed-off-by: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Acked-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Acked-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>treewide: move set_memory_* functions away from cacheflush.h</title>
<updated>2017-05-09T00:15:13+00:00</updated>
<author>
<name>Laura Abbott</name>
<email>labbott@redhat.com</email>
</author>
<published>2017-05-08T22:57:59+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=299878bac326c890699c696ebba26f56fe93fc75'/>
<id>urn:sha1:299878bac326c890699c696ebba26f56fe93fc75</id>
<content type='text'>
Patch series "set_memory_* functions header refactor", v3.

The set_memory_* APIs came out of a desire to have a better way to
change memory attributes.  Many of these attributes were linked to cache
functionality so the prototypes were put in cacheflush.h.  These days,
the APIs have grown and have a much wider use than just cache APIs.  To
support this growth, split off set_memory_* and friends into a separate
header file to avoid growing cacheflush.h for APIs that have nothing to
do with caches.

Link: http://lkml.kernel.org/r/1488920133-27229-2-git-send-email-labbott@redhat.com
Signed-off-by: Laura Abbott &lt;labbott@redhat.com&gt;
Acked-by: Russell King &lt;rmk+kernel@armlinux.org.uk&gt;
Acked-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm: add arch-independent testcases for RODATA</title>
<updated>2017-02-28T02:43:48+00:00</updated>
<author>
<name>Jinbum Park</name>
<email>jinb.park7@gmail.com</email>
</author>
<published>2017-02-27T22:30:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=2959a5f726f6510d6dd7c958f8877e08d0cf589c'/>
<id>urn:sha1:2959a5f726f6510d6dd7c958f8877e08d0cf589c</id>
<content type='text'>
This patch makes arch-independent testcases for RODATA.  Both x86 and
x86_64 already have testcases for RODATA, But they are arch-specific
because using inline assembly directly.

And cacheflush.h is not a suitable location for rodata-test related
things.  Since they were in cacheflush.h, If someone change the state of
CONFIG_DEBUG_RODATA_TEST, It cause overhead of kernel build.

To solve the above issues, write arch-independent testcases and move it
to shared location.

[jinb.park7@gmail.com: fix config dependency]
  Link: http://lkml.kernel.org/r/20170209131625.GA16954@pjb1027-Latitude-E5410
Link: http://lkml.kernel.org/r/20170129105436.GA9303@pjb1027-Latitude-E5410
Signed-off-by: Jinbum Park &lt;jinb.park7@gmail.com&gt;
Acked-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Arjan van de Ven &lt;arjan@linux.intel.com&gt;
Cc: Laura Abbott &lt;labbott@redhat.com&gt;
Cc: Russell King &lt;linux@armlinux.org.uk&gt;
Cc: Valentin Rothberg &lt;valentinrothberg@gmail.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>remove stray include of asm/uaccess.h from cacheflush.h</title>
<updated>2016-09-28T01:15:22+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2016-09-05T15:27:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=b79d8d82bb994fe6154ea1a8e56d587ef9e356ae'/>
<id>urn:sha1:b79d8d82bb994fe6154ea1a8e56d587ef9e356ae</id>
<content type='text'>
It was introduced in "arch, x86: pmem api for ensuring durability
of persistent memory updates" in July 2015, along with the code
that really used that stuff.  Three weeks later all that code
got moved to asm/pmem.h by "pmem, x86: move x86 PMEM API to new
pmem.h header"; include, however, was left behind.

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
</entry>
<entry>
<title>x86/mm: Always enable CONFIG_DEBUG_RODATA and remove the Kconfig option</title>
<updated>2016-02-22T07:51:38+00:00</updated>
<author>
<name>Kees Cook</name>
<email>keescook@chromium.org</email>
</author>
<published>2016-02-17T22:41:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=9ccaf77cf05915f51231d158abfd5448aedde758'/>
<id>urn:sha1:9ccaf77cf05915f51231d158abfd5448aedde758</id>
<content type='text'>
This removes the CONFIG_DEBUG_RODATA option and makes it always enabled.

This simplifies the code and also makes it clearer that read-only mapped
memory is just as fundamental a security feature in kernel-space as it is
in user-space.

Suggested-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Signed-off-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: David Brown &lt;david.brown@linaro.org&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: Emese Revfy &lt;re.emese@gmail.com&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Mathias Krause &lt;minipli@googlemail.com&gt;
Cc: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Cc: PaX Team &lt;pageexec@freemail.hu&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch &lt;linux-arch@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/1455748879-21872-4-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
</entry>
<entry>
<title>asm-generic: Consolidate mark_rodata_ro()</title>
<updated>2016-02-22T07:51:37+00:00</updated>
<author>
<name>Kees Cook</name>
<email>keescook@chromium.org</email>
</author>
<published>2016-02-17T22:41:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=e267d97b83d9cecc16c54825f9f3ac7f72dc1e1e'/>
<id>urn:sha1:e267d97b83d9cecc16c54825f9f3ac7f72dc1e1e</id>
<content type='text'>
Instead of defining mark_rodata_ro() in each architecture, consolidate it.

Signed-off-by: Kees Cook &lt;keescook@chromium.org&gt;
Acked-by: Will Deacon &lt;will.deacon@arm.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Andy Gross &lt;agross@codeaurora.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Ard Biesheuvel &lt;ard.biesheuvel@linaro.org&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Cc: Ashok Kumar &lt;ashoks@broadcom.com&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: David Brown &lt;david.brown@linaro.org&gt;
Cc: David Hildenbrand &lt;dahi@linux.vnet.ibm.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: Emese Revfy &lt;re.emese@gmail.com&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Helge Deller &lt;deller@gmx.de&gt;
Cc: James E.J. Bottomley &lt;jejb@parisc-linux.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Luis R. Rodriguez &lt;mcgrof@suse.com&gt;
Cc: Marc Zyngier &lt;marc.zyngier@arm.com&gt;
Cc: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Mathias Krause &lt;minipli@googlemail.com&gt;
Cc: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Cc: Nicolas Pitre &lt;nicolas.pitre@linaro.org&gt;
Cc: PaX Team &lt;pageexec@freemail.hu&gt;
Cc: Paul Gortmaker &lt;paul.gortmaker@windriver.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Cc: Russell King &lt;linux@arm.linux.org.uk&gt;
Cc: Rusty Russell &lt;rusty@rustcorp.com.au&gt;
Cc: Stephen Boyd &lt;sboyd@codeaurora.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Toshi Kani &lt;toshi.kani@hp.com&gt;
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch &lt;linux-arch@vger.kernel.org&gt;
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Link: http://lkml.kernel.org/r/1455748879-21872-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
</entry>
<entry>
<title>nd_blk: change aperture mapping from WC to WB</title>
<updated>2015-08-27T23:38:28+00:00</updated>
<author>
<name>Ross Zwisler</name>
<email>ross.zwisler@linux.intel.com</email>
</author>
<published>2015-08-27T19:14:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=67a3e8fe90156d41cd480d3dfbb40f3bc007c262'/>
<id>urn:sha1:67a3e8fe90156d41cd480d3dfbb40f3bc007c262</id>
<content type='text'>
This should result in a pretty sizeable performance gain for reads.  For
rough comparison I did some simple read testing using PMEM to compare
reads of write combining (WC) mappings vs write-back (WB).  This was
done on a random lab machine.

PMEM reads from a write combining mapping:
	# dd of=/dev/null if=/dev/pmem0 bs=4096 count=100000
	100000+0 records in
	100000+0 records out
	409600000 bytes (410 MB) copied, 9.2855 s, 44.1 MB/s

PMEM reads from a write-back mapping:
	# dd of=/dev/null if=/dev/pmem0 bs=4096 count=1000000
	1000000+0 records in
	1000000+0 records out
	4096000000 bytes (4.1 GB) copied, 3.44034 s, 1.2 GB/s

To be able to safely support a write-back aperture I needed to add
support for the "read flush" _DSM flag, as outlined in the DSM spec:

http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

This flag tells the ND BLK driver that it needs to flush the cache lines
associated with the aperture after the aperture is moved but before any
new data is read.  This ensures that any stale cache lines from the
previous contents of the aperture will be discarded from the processor
cache, and the new data will be read properly from the DIMM.  We know
that the cache lines are clean and will be discarded without any
writeback because either a) the previous aperture operation was a read,
and we never modified the contents of the aperture, or b) the previous
aperture operation was a write and we must have written back the dirtied
contents of the aperture to the DIMM before the I/O was completed.

In order to add support for the "read flush" flag I needed to add a
generic routine to invalidate cache lines, mmio_flush_range().  This is
protected by the ARCH_HAS_MMIO_FLUSH Kconfig variable, and is currently
only supported on x86.

Signed-off-by: Ross Zwisler &lt;ross.zwisler@linux.intel.com&gt;
Signed-off-by: Dan Williams &lt;dan.j.williams@intel.com&gt;
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