From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Subject: Re: radeon, apertures & memory mapping Date: Mon, 14 Mar 2005 11:41:23 +1100 Message-ID: <16948.56755.114690.200854@cargo.ozlabs.ibm.com> References: <1110677744.19810.80.camel@gaston> <20050313082216.GA7362@sci.fi> <1110705646.14684.126.camel@gaston> <20050313103936.GA11002@sci.fi> <1110715499.14684.132.camel@gaston> <9e473391050313081937cde207@mail.gmail.com> <1110750553.5787.155.camel@gaston> <9e47339105031314101c89e50e@mail.gmail.com> <1110752401.19810.177.camel@gaston> <9e47339105031315002a444f00@mail.gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit In-Reply-To: <9e47339105031315002a444f00@mail.gmail.com> Sender: dri-devel-admin@lists.sourceforge.net Errors-To: dri-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: Jon Smirl Cc: Benjamin Herrenschmidt , =?ISO-8859-1?Q?Ville_Syrj=E4l=E4?= , Jon Smirl , dri-devel@lists.sourceforge.net, Linux Fbdev development list , xorg@lists.freedesktop.org Jon Smirl writes: > > It works, but it's illegal. That means that the CPU might well speculate > > a load from one of these pages in kernel-land just because it happens to > > be next to a page where you are iterating an array, and may then bring a > > bit in the cache from that page. > > That shouldn't matter the page brought in would be for a speculative > read and never accessed. It should just fall out of the cache and not > be written back. There is only one cachable mapping. In this model > writes are always followed by a flush before telling the GPU to access > the memory that has just been written. That would be fine, but it would mean making sure that every time any code in the DRI, DRM or X server writes to the AGP memory, it does the flush as well. Sounds like a maintenance nightmare to me... Paul. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click --