lkml.org 
[lkml]   [2018]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Subject[PATCH v3 0/9] Series short description
From
Date
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

\
 
 \ /
  Last update: 2018-05-04 02:16    [W:0.076 / U:0.984 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site