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 ESMTP id 4CF49DDF6E for ; Thu, 22 Mar 2007 23:01:51 +1100 (EST) Subject: Re: [PATCH 2/4] powerpc: Fix 32 bits mm operations when not using BATs From: Benjamin Herrenschmidt To: Segher Boessenkool In-Reply-To: <1174564853.10836.39.camel@localhost.localdomain> References: <20070322030114.D5B9FDDF2B@ozlabs.org> <3839ac2050c6dcf8c0062b4a367b2ba9@kernel.crashing.org> <1174564853.10836.39.camel@localhost.localdomain> Content-Type: text/plain Date: Thu, 22 Mar 2007 23:01:40 +1100 Message-Id: <1174564900.10836.41.camel@localhost.localdomain> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Paul Mackerras List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2007-03-22 at 23:00 +1100, Benjamin Herrenschmidt wrote: > On Thu, 2007-03-22 at 12:55 +0100, Segher Boessenkool wrote: > > > + * If the hash table bucket is full of kernel text entries, we'll > > > + * lockup here but that shouldn't happen > > > > On 32-bit we have room for one HPTE per real page -- assuming > > the kernel text is fully enclosed inside one power-of-two > > size and aligned range of address space (i.e. always ;-) ), > > a lockup here _cannot_ happen. It doesn't get tight until you > > start using all of memory as kernel text. > > I know, which is why "shouldn't" is a good enough choice of word :-) > > > So replace this comment with something like "the HTAB is > > sized such that no PTEG can overflow from kernel text alone"? > > It sounds a lot less hand-wavy than "but this shouldn't happen". Note that there is still a potential of a second entry due to the secondary group but that wouldn't happen in practice :-) Ben.