Ingo, Thomas, Al, any concerns with this series? On Thu, May 3, 2018 at 5:06 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > 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 > _______________________________________________ > Linux-nvdimm mailing list > Linux-nvdimm@xxxxxxxxxxxx > https://lists.01.org/mailman/listinfo/linux-nvdimm
