From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Gabriel Paubert <paubert@iram.es>
Cc: debian-powerpc@lists.debian.org, linuxppc-dev@ozlabs.org
Subject: Re: Not coherent cache DMA for G3/G4 CPUs: clarification needed
Date: Fri, 21 Apr 2006 10:09:14 +1000 [thread overview]
Message-ID: <1145578154.4517.15.camel@localhost.localdomain> (raw)
In-Reply-To: <20060420234640.GA20059@iram.es>
> In this case the problem is double mapping with inconsistent attributes
> (through BAT and page tables I assume).
Yes.
> > On POWER4, 970 and later, the chip guys confirmed that the problem is
> > real though. Not only bcs of prefetch but also speculative execution
> > which can cause the chip to do a load that will never actually be
> > executed. Imagine for example a loop walking an array, the chip might
> > speculatively load elements beyond the array by speculatively executing
> > beyond the branch that ends the loop.
>
> Even if the page has the guarded bit set?
The BAT mapping doesn't have G set.
Ben.
next prev parent reply other threads:[~2006-04-21 0:09 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-20 18:57 Not coherent cache DMA for G3/G4 CPUs: clarification needed Gerhard Pircher
2006-04-20 20:38 ` Eugene Surovegin
2006-04-20 20:56 ` Gerhard Pircher
2006-04-20 21:02 ` Eugene Surovegin
2006-04-20 21:10 ` Gerhard Pircher
2006-04-20 21:55 ` Eugene Surovegin
2006-04-20 22:08 ` Gerhard Pircher
2006-04-24 19:21 ` Mark A. Greer
2006-04-21 4:38 ` Benjamin Herrenschmidt
2006-04-21 8:03 ` Gerhard Pircher
2006-04-21 14:33 ` Brent Cook
2006-04-21 21:51 ` Benjamin Herrenschmidt
2006-04-27 21:31 ` Mark A. Greer
2006-04-27 21:53 ` Benjamin Herrenschmidt
2006-04-27 22:08 ` Mark A. Greer
2006-04-29 17:57 ` Gerhard Pircher
2006-04-20 21:06 ` Benjamin Herrenschmidt
2006-04-20 21:13 ` Eugene Surovegin
2006-04-20 21:19 ` Eugene Surovegin
2006-04-20 22:40 ` Benjamin Herrenschmidt
2006-04-20 22:39 ` Benjamin Herrenschmidt
2006-04-20 23:46 ` Gabriel Paubert
2006-04-21 0:09 ` Benjamin Herrenschmidt [this message]
2006-04-20 21:33 ` Eugene Surovegin
2006-04-20 22:41 ` Benjamin Herrenschmidt
2006-04-21 8:21 ` Gerhard Pircher
2006-04-20 21:03 ` Benjamin Herrenschmidt
2006-04-20 21:33 ` Gerhard Pircher
2006-04-20 22:07 ` Gabriel Paubert
2006-04-20 22:26 ` Gerhard Pircher
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