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Message-ID: <160087928642.3520.17063139768910633998.stgit@dwillia2-desk3.amr.corp.intel.com>
Date: Wed, 23 Sep 2020 09:41:26 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: mingo@...hat.com
Cc: Tony Luck <tony.luck@...el.com>, Vivek Goyal <vgoyal@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Borislav Petkov <bp@...en8.de>, stable@...r.kernel.org,
x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Paul Mackerras <paulus@...ba.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Erwin Tsaur <erwin.tsaur@...el.com>,
Michael Ellerman <mpe@...erman.id.au>,
Mikulas Patocka <mpatocka@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
0day robot <lkp@...el.com>, tglx@...utronix.de, x86@...nel.org,
linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
jack@...e.cz
Subject: [PATCH v9 0/2] Renovate memcpy_mcsafe with copy_mc_to_{user, kernel}
Changes since v8 [1]:
- Rebase on v5.9-rc6
- Fix a performance regression in the x86 copy_mc_to_user()
implementation that was duplicating copies in the "fragile" case.
- Refreshed the cover letter.
[1]: http://lore.kernel.org/r/159630255616.3143511.18110575960499749012.stgit@dwillia2-desk3.amr.corp.intel.com
---
The motivations to go rework memcpy_mcsafe() are that the benefit of
doing slow and careful copies is obviated on newer CPUs, and that the
current opt-in list of cpus to instrument recovery is broken relative to
those cpus. There is no need to keep an opt-in list up to date on an
ongoing basis if pmem/dax operations are instrumented for recovery by
default. With recovery enabled by default the old "mcsafe_key" opt-in to
careful copying can be made a "fragile" opt-out. Where the "fragile"
list takes steps to not consume poison across cachelines.
The discussion with Linus made clear that the current "_mcsafe" suffix
was imprecise to a fault. The operations that are needed by pmem/dax are
to copy from a source address that might throw #MC to a destination that
may write-fault, if it is a user page. So copy_to_user_mcsafe() becomes
copy_mc_to_user() to indicate the separate precautions taken on source
and destination. copy_mc_to_kernel() is introduced as a version that
does not expect write-faults on the destination, but is still prepared
to abort with an error code upon taking #MC.
These patches have received a kbuild-robot build success notification
across 114 configs, the rebase to v5.9-rc6 did not encounter any
conflicts, and the merge with tip/master is conflict-free.
---
Dan Williams (2):
x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user,kernel}()
x86/copy_mc: Introduce copy_mc_generic()
arch/powerpc/Kconfig | 2
arch/powerpc/include/asm/string.h | 2
arch/powerpc/include/asm/uaccess.h | 40 +++--
arch/powerpc/lib/Makefile | 2
arch/powerpc/lib/copy_mc_64.S | 4
arch/x86/Kconfig | 2
arch/x86/Kconfig.debug | 2
arch/x86/include/asm/copy_mc_test.h | 75 +++++++++
arch/x86/include/asm/mcsafe_test.h | 75 ---------
arch/x86/include/asm/string_64.h | 32 ----
arch/x86/include/asm/uaccess.h | 21 +++
arch/x86/include/asm/uaccess_64.h | 20 --
arch/x86/kernel/cpu/mce/core.c | 8 -
arch/x86/kernel/quirks.c | 9 -
arch/x86/lib/Makefile | 1
arch/x86/lib/copy_mc.c | 65 ++++++++
arch/x86/lib/copy_mc_64.S | 165 ++++++++++++++++++++
arch/x86/lib/memcpy_64.S | 115 --------------
arch/x86/lib/usercopy_64.c | 21 ---
drivers/md/dm-writecache.c | 15 +-
drivers/nvdimm/claim.c | 2
drivers/nvdimm/pmem.c | 6 -
include/linux/string.h | 9 -
include/linux/uaccess.h | 9 +
include/linux/uio.h | 10 +
lib/Kconfig | 7 +
lib/iov_iter.c | 43 +++--
tools/arch/x86/include/asm/mcsafe_test.h | 13 --
tools/arch/x86/lib/memcpy_64.S | 115 --------------
tools/objtool/check.c | 5 -
tools/perf/bench/Build | 1
tools/perf/bench/mem-memcpy-x86-64-lib.c | 24 ---
tools/testing/nvdimm/test/nfit.c | 48 +++---
.../testing/selftests/powerpc/copyloops/.gitignore | 2
tools/testing/selftests/powerpc/copyloops/Makefile | 6 -
.../selftests/powerpc/copyloops/copy_mc_64.S | 1
.../selftests/powerpc/copyloops/memcpy_mcsafe_64.S | 1
37 files changed, 452 insertions(+), 526 deletions(-)
rename arch/powerpc/lib/{memcpy_mcsafe_64.S => copy_mc_64.S} (98%)
create mode 100644 arch/x86/include/asm/copy_mc_test.h
delete mode 100644 arch/x86/include/asm/mcsafe_test.h
create mode 100644 arch/x86/lib/copy_mc.c
create mode 100644 arch/x86/lib/copy_mc_64.S
delete mode 100644 tools/arch/x86/include/asm/mcsafe_test.h
delete mode 100644 tools/perf/bench/mem-memcpy-x86-64-lib.c
create mode 120000 tools/testing/selftests/powerpc/copyloops/copy_mc_64.S
delete mode 120000 tools/testing/selftests/powerpc/copyloops/memcpy_mcsafe_64.S
base-commit: ba4f184e126b751d1bffad5897f263108befc780
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