From: Dan Williams <dan.j.williams@intel.com>
To: linux-nvdimm <linux-nvdimm@lists.01.org>
Cc: "Luck, Tony" <tony.luck@intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mike Snitzer" <snitzer@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"X86 ML" <x86@kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Andy Lutomirski" <luto@amacapital.net>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Mika Penttilä" <mika.penttila@nextfour.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Christoph Hellwig" <hch@lst.de>,
"Al Viro" <viro@zeniv.linux.org.uk>
Subject: use memcpy_mcsafe() for copy_to_iter() (was: Re: [PATCH v3 0/9] Series short description)
Date: Fri, 11 May 2018 10:10:22 -0700 [thread overview]
Message-ID: <CAPcyv4g5p72aiXYh8Tf03tvZq8HNYmTFU95PJGG1iQ4JHcr9PA@mail.gmail.com> (raw)
Ingo, Thomas, Al, any concerns with this series?
On Thu, May 3, 2018 at 5:06 PM, Dan Williams <dan.j.williams@intel.com> 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@lists.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm
next reply other threads:[~2018-05-11 17:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-11 17:10 Dan Williams [this message]
2018-05-14 7:26 ` use memcpy_mcsafe() for copy_to_iter() (was: Re: [PATCH v3 0/9] Series short description) Ingo Molnar
2018-05-14 15:52 ` Dan Williams
2018-05-14 17:53 ` Andy Lutomirski
2018-05-14 19:20 ` Linus Torvalds
2018-05-15 6:49 ` Ingo Molnar
2018-05-15 17:20 ` Dan Williams
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