Re: [RFC PATCH] membarrier-sync-core: Document architecture support

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

----- On Feb 6, 2018, at 11:51 AM, efficios efficios@ubuntu.efficios.com wrote:

> Ensure we gather architecture requirements about each architecture supporting
> the "sync_core" membarrier command in a single file under
> Documentation/features.
> 
> [ This patch applies on top of tip sched/core. ]

please disregard this email. I will fix my git config on this dev machine and
re-send.

Thanks,

Mathieu

> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> 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: H. Peter Anvin <hpa@zytor.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: Russell King <linux@armlinux.org.uk>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: linux-api@vger.kernel.org
> Cc: linux-arch@vger.kernel.org
> ---
> .../sched/membarrier-sync-core/arch-support.txt    | 62 ++++++++++++++++++++++
> 1 file changed, 62 insertions(+)
> create mode 100644
> Documentation/features/sched/membarrier-sync-core/arch-support.txt
> 
> diff --git a/Documentation/features/sched/membarrier-sync-core/arch-support.txt
> b/Documentation/features/sched/membarrier-sync-core/arch-support.txt
> new file mode 100644
> index 0000000..2c815a7
> --- /dev/null
> +++ b/Documentation/features/sched/membarrier-sync-core/arch-support.txt
> @@ -0,0 +1,62 @@
> +#
> +# 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 |
> +    -----------------------
> --
> 1.9.1

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com