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

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Date:   Tue, 6 Feb 2018 16:58:04 +0000 (UTC)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrea Parri <parri.andrea@...il.com>,
        Andrew Hunter <ahh@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Avi Kivity <avi@...lladb.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Dave Watson <davejwatson@...com>, David Sehr <sehr@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        maged michael <maged.michael@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        "Russell King, ARM Linux" <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>,
        linux-api <linux-api@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [RFC PATCH] membarrier-sync-core: Document architecture support

----- On Feb 6, 2018, at 11:51 AM, efficios efficios@...ntu.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@...icios.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Andrea Parri <parri.andrea@...il.com>
> Cc: Andrew Hunter <ahh@...gle.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Avi Kivity <avi@...lladb.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: Dave Watson <davejwatson@...com>
> Cc: David Sehr <sehr@...gle.com>
> Cc: Greg Hackmann <ghackmann@...gle.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Maged Michael <maged.michael@...il.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Will Deacon <will.deacon@....com>
> Cc: linux-api@...r.kernel.org
> Cc: linux-arch@...r.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