From: Michael Ellerman <mpe@ellerman.id.au>
To: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Cc: paulmck@kernel.org, linux-kernel@vger.kernel.org,
Rohan McLure <rmclure@linux.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] arch/powerpc/include/asm/barrier.h: redefine rmb and wmb to lwsync
Date: Thu, 23 Feb 2023 20:24:34 +1100 [thread overview]
Message-ID: <871qmgbup9.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <Y/bvClrV60CXK79G@li-a450e7cc-27df-11b2-a85c-b5a9ac31e8ef.ibm.com>
Kautuk Consul <kconsul@linux.vnet.ibm.com> writes:
>
>> You are correct, the patch is wrong because it fails to account for IO
>> accesses.
>
> Okay, I looked at the PowerPC ISA and found:
> "The memory barrier provides an ordering function for the storage accesses
> caused by Load, Store,and dcbz instructions that are executed by the processor
> executing the sync instruction and for which the specified storage location
> is in storage that is Memory Coherence Required and is neither Write Through
> Required nor Caching Inhibited.
Yep, that's the key sentence there. If you look at the definition for
"sync" it has not exceptions for different storage types.
I agree it's not very clear unless you're looking closely.
> Thanks for your time, Michael. Sorry for the noise.
>>
>> Kautuk, I'm not sure what motivated you to look at these barriers, was
>> it just the documentation you linked to?
> I read the basic documentation. Now that I have access to the PowerISA
> document I guess I'll go through it more thoroughly.
The ISA is available publicly. There's links to most versions here:
https://wiki.raptorcs.com/wiki/Power_ISA
cheers
next prev parent reply other threads:[~2023-02-23 9:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-22 9:03 [PATCH v2] arch/powerpc/include/asm/barrier.h: redefine rmb and wmb to lwsync Kautuk Consul
2023-02-22 9:30 ` Kautuk Consul
2023-02-22 9:44 ` Christophe Leroy
2023-02-22 9:49 ` Kautuk Consul
2023-02-22 9:43 ` Christophe Leroy
2023-02-22 9:46 ` Kautuk Consul
2023-02-22 9:51 ` Christophe Leroy
2023-02-22 9:55 ` Kautuk Consul
2023-02-22 17:47 ` Paul E. McKenney
2023-02-23 3:51 ` Michael Ellerman
2023-02-23 4:07 ` Kautuk Consul
2023-02-23 4:43 ` Kautuk Consul
2023-02-23 9:24 ` Michael Ellerman [this message]
2023-02-23 4:01 ` Kautuk Consul
2023-02-23 4:16 ` Paul E. McKenney
2023-02-23 4:22 ` Kautuk Consul
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