From: Adrian Cox <adrian@humboldt.co.uk>
To: Tom Rini <trini@kernel.crashing.org>
Cc: linuxppc-dev@lists.linuxppc.org
Subject: Re: New 745x errata
Date: 17 Nov 2003 15:34:05 +0000 [thread overview]
Message-ID: <1069083245.10537.58.camel@newt> (raw)
In-Reply-To: <20031117150409.GA30251@ip68-0-152-218.tc.ph.cox.net>
On Mon, 2003-11-17 at 15:04, Tom Rini wrote:
> On Mon, Nov 17, 2003 at 02:57:53PM +0000, Adrian Cox wrote:
> > Any opinion on the dcbt issue? It looks like it could provide a way for
> > a malicious userspace application to crash the machine, though it needs
> > a combination of:
> > 1) good timing
> > 2) a peripheral that would be confused by an extra read cycle
> It depends on what the fix is. For example, Linus just fixed a
> theoretical race that has a 1-3 cycle (depending on x86 cpu I think he
> said) race because he happened to be in there anyhow (and it turns out
> the fix is easy).
The fix is simple, but carries a performance cost: set the HID0_NOPTI
bit and disable all dcbt instructions. The kernel uses dcbt instructions
in a lot of places, but copy_page is what matters the most.
A copy_page routine using dst instructions might be faster anyway, and
would be immune to this problem.
On closer reading, I now think this problem may be harmless - see my
explanation to Gabriel Paubert for more details.
- Adrian Cox
http://www.humboldt.co.uk/
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2003-11-17 15:34 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-13 11:05 New 745x errata Adrian Cox
2003-11-14 10:40 ` Giuliano Pochini
2003-11-14 11:00 ` Adrian Cox
2003-11-14 16:24 ` Tom Rini
2003-11-17 14:57 ` Adrian Cox
2003-11-17 15:04 ` Tom Rini
2003-11-17 15:34 ` Adrian Cox [this message]
2003-11-18 8:40 ` Giuliano Pochini
2003-11-17 15:12 ` Gabriel Paubert
2003-11-17 15:37 ` Adrian Cox
2003-11-17 15:49 ` Gabriel Paubert
2003-11-17 17:05 ` Gabriel Paubert
2003-11-17 17:34 ` Jon Masters
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