linux/arch/x86
Dan Williams 0aed55af88 x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations
The pmem driver has a need to transfer data with a persistent memory
destination and be able to rely on the fact that the destination writes are not
cached. It is sufficient for the writes to be flushed to a cpu-store-buffer
(non-temporal / "movnt" in x86 terms), as we expect userspace to call fsync()
to ensure data-writes have reached a power-fail-safe zone in the platform. The
fsync() triggers a REQ_FUA or REQ_FLUSH to the pmem driver which will turn
around and fence previous writes with an "sfence".

Implement a __copy_from_user_inatomic_flushcache, memcpy_page_flushcache, and
memcpy_flushcache, that guarantee that the destination buffer is not dirty in
the cpu cache on completion. The new copy_from_iter_flushcache and sub-routines
will be used to replace the "pmem api" (include/linux/pmem.h +
arch/x86/include/asm/pmem.h). The availability of copy_from_iter_flushcache()
and memcpy_flushcache() are gated by the CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
config symbol, and fallback to copy_from_iter_nocache() and plain memcpy()
otherwise.

This is meant to satisfy the concern from Linus that if a driver wants to do
something beyond the normal nocache semantics it should be something private to
that driver [1], and Al's concern that anything uaccess related belongs with
the rest of the uaccess code [2].

The first consumer of this interface is a new 'copy_from_iter' dax operation so
that pmem can inject cache maintenance operations without imposing this
overhead on other dax-capable drivers.

[1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html
[2]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009942.html

Cc: <x86@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2017-06-09 09:09:56 -07:00
..
boot x86/boot: Use CROSS_COMPILE prefix for readelf 2017-05-21 13:04:27 +02:00
configs Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-01 20:51:12 -07:00
crypto crypto: glue_helper - remove the le128_gf128mul_x_ble function 2017-04-05 21:58:37 +08:00
entry Revert "x86/entry: Fix the end of the stack for newly forked tasks" 2017-05-24 09:05:16 +02:00
events perf/core improvements and fixes: 2017-05-03 19:28:27 +02:00
hyperv char/misc patches for 4.12-rc1 2017-05-04 19:15:35 -07:00
ia32 sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
include x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations 2017-06-09 09:09:56 -07:00
kernel x86/debug/32: Convert a smp_processor_id() call to raw to avoid DEBUG_PREEMPT warning 2017-05-29 08:22:49 +02:00
kvm KVM: x86: Fix nmi injection failure when vcpu got blocked 2017-06-01 11:23:10 +02:00
lguest Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-01 20:51:12 -07:00
lib x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations 2017-06-09 09:09:56 -07:00
math-emu Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
mm Revert "x86/PAT: Fix Xorg regression on CPUs that don't support PAT" 2017-06-01 15:52:23 +02:00
net x86: use set_memory.h header 2017-05-08 17:15:13 -07:00
oprofile
pci pci-v4.12-changes 2017-05-08 19:03:25 -07:00
platform x86/efi: Correct EFI identity mapping under 'efi=old_map' when KASLR is enabled 2017-05-28 11:06:16 +02:00
power x86/mm: Add support for gbpages to kernel_ident_mapping_init() 2017-05-08 08:28:40 +02:00
purgatory kasan: do not sanitize kexec purgatory 2017-03-31 17:13:30 -07:00
ras RAS: Add a Corrected Errors Collector 2017-03-28 08:54:48 +02:00
realmode x86: use set_memory.h header 2017-05-08 17:15:13 -07:00
tools x86/tools: Fix gcc-7 warning in relocs.c 2016-12-19 11:50:24 +01:00
um Merge branch 'for-linus-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml 2017-05-13 10:20:02 -07:00
video
xen xen: make xen_flush_tlb_all() static 2017-05-19 08:04:25 +02:00
.gitignore
Kbuild Drivers: hv vmbus: Move Hypercall page setup out of common code 2017-01-19 11:42:07 +01:00
Kconfig x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations 2017-06-09 09:09:56 -07:00
Kconfig.cpu
Kconfig.debug usb/early: Add driver for xhci debug capability 2017-03-21 12:30:05 +01:00
Makefile x86/build: Permit building with old make versions 2017-05-24 09:05:17 +02:00
Makefile_32.cpu x86/build: Mostly disable '-maccumulate-outgoing-args' 2017-03-30 11:53:04 +02:00
Makefile.um