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Date:   Wed, 16 Jun 2021 16:48:54 -0700
From:   "Andy Lutomirski" <luto@kernel.org>
To:     "Nicholas Piggin" <npiggin@gmail.com>,
        "the arch/x86 maintainers" <x86@kernel.org>
Cc:     "Andrew Morton" <akpm@linux-foundation.org>,
        "Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
        "Catalin Marinas" <catalin.marinas@arm.com>,
        "Dave Hansen" <dave.hansen@intel.com>,
        linux-arm-kernel@lists.infradead.org,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
        "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
        "Michael Ellerman" <mpe@ellerman.id.au>,
        "Paul Mackerras" <paulus@samba.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        stable@vger.kernel.org, "Will Deacon" <will@kernel.org>
Subject: =?UTF-8?Q?Re:_[PATCH_8/8]_membarrier:_Rewrite_sync=5Fcore=5Fbefore=5Fuse?=
 =?UTF-8?Q?rmode()_and_improve_documentation?=
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On Wed, Jun 16, 2021, at 11:52 AM, Andy Lutomirski wrote:
> On 6/15/21 9:45 PM, Nicholas Piggin wrote:
> > Excerpts from Andy Lutomirski's message of June 16, 2021 1:21 pm:
> >> The old sync_core_before_usermode() comments suggested that a non-icache-syncing
> >> return-to-usermode instruction is x86-specific and that all other
> >> architectures automatically notice cross-modified code on return to
> >> userspace.
> 
> >> +/*
> >> + * XXX: can a powerpc person put an appropriate comment here?
> >> + */
> >> +static inline void membarrier_sync_core_before_usermode(void)
> >> +{
> >> +}
> >> +
> >> +#endif /* _ASM_POWERPC_SYNC_CORE_H */
> > 
> > powerpc's can just go in asm/membarrier.h
> 
> $ ls arch/powerpc/include/asm/membarrier.h
> ls: cannot access 'arch/powerpc/include/asm/membarrier.h': No such file
> or directory

Which is because I deleted it.  Duh.  I'll clean this up.

> 
> 
> > 
> > /*
> >  * The RFI family of instructions are context synchronising, and
> >  * that is how we return to userspace, so nothing is required here.
> >  */
> 
> Thanks!
>