linux-kernel - Re: Opinion on ordering of writel vs. stores to RAM

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: <1158045420.15465.97.camel@localhost.localdomain>
Date:	Tue, 12 Sep 2006 17:17:00 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Albert Cahalan <acahalan@...il.com>
Cc:	jbarnes@...tuousgeek.org, alan@...rguk.ukuu.org.uk,
	davem@...emloft.net, jeff@...zik.org, paulus@...ba.org,
	torvalds@...l.org, linux-kernel@...r.kernel.org, akpm@...l.org,
	segher@...nel.crashing.org
Subject: Re: Opinion on ordering of writel vs. stores to RAM


> If I see an io_to_io_barrier(), how am I to tell if it is
> read to read, write to write, read to write, write to read,
> read/write to read, read/write to write, read to read/write,
> write to read/write, or read/write to read/write?
> 
> Considering just reads and writes to MMIO, there are
> 9 possible types of fence. SPARC seems to cover a
> decent number of these distinctly; the instruction takes
> an immediate value as flags.

We need to decide wether a single one doing a full MMIO fence (and not
memory) is enough or if the performance different justifies maybe having
io_to_io_{wmb,rmb,mb}. I don't see any real use for more combinations.

David ? It's your call here. What do you think ?

Ben.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/