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membarrier-sync-core: Document architecture support

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Ensure we gather architecture requirements about each architecture
supporting the "sync_core" membarrier command in a single file under
Documentation/features.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Hunter <ahh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: David Sehr <sehr@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maged Michael <maged.michael@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-api@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/1518208256-22034-1-git-send-email-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mathieu Desnoyers 2018-02-09 15:30:56 -05:00 committed by Ingo Molnar
parent f1517df870
commit 6a546c7e69
1 changed files with 62 additions and 0 deletions
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62
Documentation/features/sched/membarrier-sync-core/arch-support.txt Normal file
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#
# Feature name: membarrier-sync-core
# Kconfig: ARCH_HAS_MEMBARRIER_SYNC_CORE
# description: arch supports core serializing membarrier
#
# Architecture requirements
#
# * arm64
#
# Rely on eret context synchronization when returning from IPI handler, and
# when returning to user-space.
#
# * x86
#
# x86-32 uses IRET as return from interrupt, which takes care of the IPI.
# However, it uses both IRET and SYSEXIT to go back to user-space. The IRET
# instruction is core serializing, but not SYSEXIT.
#
# x86-64 uses IRET as return from interrupt, which takes care of the IPI.
# However, it can return to user-space through either SYSRETL (compat code),
# SYSRETQ, or IRET.
#
# Given that neither SYSRET{L,Q}, nor SYSEXIT, are core serializing, we rely
# instead on write_cr3() performed by switch_mm() to provide core serialization
# after changing the current mm, and deal with the special case of kthread ->
# uthread (temporarily keeping current mm into active_mm) by issuing a
# sync_core_before_usermode() in that specific case.
#
-----------------------
| arch |status|
-----------------------
| alpha: | TODO |
| arc: | TODO |
| arm: | TODO |
| arm64: | ok |
| blackfin: | TODO |
| c6x: | TODO |
| cris: | TODO |
| frv: | TODO |
| h8300: | TODO |
| hexagon: | TODO |
| ia64: | TODO |
| m32r: | TODO |
| m68k: | TODO |
| metag: | TODO |
| microblaze: | TODO |
| mips: | TODO |
| mn10300: | TODO |
| nios2: | TODO |
| openrisc: | TODO |
| parisc: | TODO |
| powerpc: | TODO |
| s390: | TODO |
| score: | TODO |
| sh: | TODO |
| sparc: | TODO |
| tile: | TODO |
| um: | TODO |
| unicore32: | TODO |
| x86: | ok |
| xtensa: | TODO |
-----------------------