linux-kernel - Re: [PATCH 1/6] MIPS: Octeon: Implement __smp_store

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b00f945a-1278-5fd2-321c-6ea5f07be128@nokia.com>
Date:   Thu, 28 Jan 2021 12:52:22 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Paul Burton <paul.burton@...tec.com>, linux-mips@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] MIPS: Octeon: Implement __smp_store_release()

Hello Peter,

On 28/01/2021 12:33, Peter Zijlstra wrote:
> This, from commit 6b07d38aaa52 ("MIPS: Octeon: Use optimized memory
> barrier primitives."):
> 
> 	#define smp_mb__before_llsc() smp_wmb()
> 	#define __smp_mb__before_llsc() __smp_wmb()
> 
> is also dodgy as hell and really wants a comment too. I'm not buying the
> Changelog of that commit either, __smp_mb__before_llsc should also
> ensure the LL cannot happen earlier, but SYNCW has no effect on loads.
> So what stops the load from being speculated?

hmm, the commit message you point to above, says:

"Since Octeon does not do speculative reads, this functions as a full barrier."

-- 
Best regards,
Alexander Sverdlin.