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From: Dan Williams <dan.j.williams@intel.com>
To: linux-nvdimm@lists.01.org
Cc: "Tony Luck" <tony.luck@intel.com>,
	"Mika Penttilä" <mika.penttila@nextfour.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Borislav Petkov" <bp@alien8.de>,
	"Mike Snitzer" <snitzer@redhat.com>,
	x86@kernel.org, "Thomas Gleixner" <tglx@linutronix.de>,
	"Christoph Hellwig" <hch@lst.de>,
	"Ross Zwisler" <ross.zwisler@linux.intel.com>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, tony.luck@intel.com,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH v3 0/9] Series short description
Date: Thu, 03 May 2018 17:06:05 -0700	[thread overview]
Message-ID: <152539236455.31796.7516599166555186700.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)

Changes since v2 [1]:

* Fix source address increment in mcsafe_handle_tail() (Mika)

* Extend the unit test to inject simulated write faults and validate
  that data is properly transferred.

* Rename MCSAFE_DEBUG to MCSAFE_TEST

[1]: https://lists.01.org/pipermail/linux-nvdimm/2018-May/015583.html

---

Currently memcpy_mcsafe() is only deployed in the pmem driver when
reading through a /dev/pmemX block device. However, a filesystem in dax
mode mounted on a /dev/pmemX block device will bypass the block layer
and the driver for reads. The filesystem-dax (fsdax) read case uses
dax_direct_access() and copy_to_iter() to bypass the block layer.

The result of the bypass is that the kernel treats machine checks during
read as system fatal (reboot) when they could simply be flagged as an
I/O error, similar to performing reads through the pmem driver. Prevent
this fatal condition by deploying memcpy_mcsafe() in the fsdax read
path.

The main differences between this copy_to_user_mcsafe() and
copy_user_generic_unrolled() are:

* Typical tail/residue handling after a fault retries the copy
  byte-by-byte until the fault happens again. Re-triggering machine
  checks is potentially fatal so the implementation uses source alignment
  and poison alignment assumptions to avoid re-triggering machine
  checks.

* SMAP coordination is handled external to the assembly with
  __uaccess_begin() and __uaccess_end().

* ITER_KVEC and ITER_BVEC can now end prematurely with an error.

The new MCSAFE_TEST facility is proposed as a way to unit test the
exception handling without requiring an ACPI EINJ capable platform.

---

Dan Williams (9):
      x86, memcpy_mcsafe: remove loop unrolling
      x86, memcpy_mcsafe: add labels for write fault handling
      x86, memcpy_mcsafe: return bytes remaining
      x86, memcpy_mcsafe: add write-protection-fault handling
      x86, memcpy_mcsafe: define copy_to_iter_mcsafe()
      dax: introduce a ->copy_to_iter dax operation
      dax: report bytes remaining in dax_iomap_actor()
      pmem: switch to copy_to_iter_mcsafe()
      x86, nfit_test: unit test for memcpy_mcsafe()


 arch/x86/Kconfig                   |    1 
 arch/x86/Kconfig.debug             |    3 +
 arch/x86/include/asm/mcsafe_test.h |   75 ++++++++++++++++++++++++
 arch/x86/include/asm/string_64.h   |   10 ++-
 arch/x86/include/asm/uaccess_64.h  |   14 +++++
 arch/x86/lib/memcpy_64.S           |  112 +++++++++++++++++-------------------
 arch/x86/lib/usercopy_64.c         |   21 +++++++
 drivers/dax/super.c                |   10 +++
 drivers/md/dm-linear.c             |   16 +++++
 drivers/md/dm-log-writes.c         |   15 +++++
 drivers/md/dm-stripe.c             |   21 +++++++
 drivers/md/dm.c                    |   25 ++++++++
 drivers/nvdimm/claim.c             |    3 +
 drivers/nvdimm/pmem.c              |   13 +++-
 drivers/s390/block/dcssblk.c       |    7 ++
 fs/dax.c                           |   21 ++++---
 include/linux/dax.h                |    5 ++
 include/linux/device-mapper.h      |    5 +-
 include/linux/string.h             |    4 +
 include/linux/uio.h                |   15 +++++
 lib/iov_iter.c                     |   61 ++++++++++++++++++++
 tools/testing/nvdimm/test/nfit.c   |  104 +++++++++++++++++++++++++++++++++
 22 files changed, 482 insertions(+), 79 deletions(-)
 create mode 100644 arch/x86/include/asm/mcsafe_test.h

             reply	other threads:[~2018-05-04  0:16 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-04  0:06 Dan Williams [this message]
2018-05-04  0:06 ` [PATCH v3 1/9] x86, memcpy_mcsafe: remove loop unrolling Dan Williams
2018-05-04  0:06 ` [PATCH v3 2/9] x86, memcpy_mcsafe: add labels for write fault handling Dan Williams
2018-05-04  0:06 ` [PATCH v3 3/9] x86, memcpy_mcsafe: return bytes remaining Dan Williams
2018-05-04  0:06 ` [PATCH v3 4/9] x86, memcpy_mcsafe: add write-protection-fault handling Dan Williams
2018-05-04  0:06 ` [PATCH v3 5/9] x86, memcpy_mcsafe: define copy_to_iter_mcsafe() Dan Williams
2018-05-04  0:06 ` [PATCH v3 6/9] dax: introduce a ->copy_to_iter dax operation Dan Williams
2018-05-23 16:13   ` Ross Zwisler
2018-05-04  0:06 ` [PATCH v3 7/9] dax: report bytes remaining in dax_iomap_actor() Dan Williams
2018-05-23 16:34   ` Ross Zwisler
2018-05-23 16:39     ` Dan Williams
2018-05-23 16:47       ` Ross Zwisler
2018-05-23 16:53         ` Dan Williams
2018-05-23 17:04           ` Ross Zwisler
2018-05-04  0:06 ` [PATCH v3 8/9] pmem: switch to copy_to_iter_mcsafe() Dan Williams
2018-05-23 16:35   ` Ross Zwisler
2018-05-04  0:06 ` [PATCH v3 9/9] x86, nfit_test: unit test for memcpy_mcsafe() Dan Williams

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