From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id CD23E2C00DC for ; Sun, 8 Dec 2013 07:59:13 +1100 (EST) Message-ID: <1386449914.21910.109.camel@pasglop> Subject: Re: [PATCH] powerpc 8xx: Loading kernels over 8Mbytes without CONFIG_PIN_TLB From: Benjamin Herrenschmidt To: christophe leroy Date: Sun, 08 Dec 2013 07:58:34 +1100 In-Reply-To: <52A2ECE4.3050407@c-s.fr> References: <20131127110406.6DC8E1A504F@localhost.localdomain> <1386356996.7375.120.camel@snotra.buserror.net> <52A2ECE4.3050407@c-s.fr> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Scott Wood , linuxppc-dev@lists.ozlabs.org, Paul Mackerras , linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, 2013-12-07 at 10:39 +0100, christophe leroy wrote: > Function setup_initial_memory_limit() in mm/init_32.c defines the > limits > based on the parameters given by the bootloader. > As far as I know, the 8xx doesn't do speculative access just because > an area is loaded in a TLB Entry. Speculative accesses are ... speculative :-) The address used for such an access can be anything really. So yes, architecturally, powerpc processors can access *anything* speculatively just because there's a valid non-garded translation. Whether the 8xx does it at all, I don't know. 44x originally did but that was so buggy that we had to force G on all mappings (until later versions of the core just burned the feature out). Pretty much all other powerpc's do it. Cheers, Ben.