Dave Airlie wrote: > On 10/31/07, Thomas Hellström <[EMAIL PROTECTED]> wrote: > >> Dave, >> >> When starting out with TTM i did look a little at AGP caching issues and >> there was an issue with cached memory and speculative pre-fetching that >> may affect the mapped-cached memory, >> and that we need to know about but perhaps ignore. >> >> Suppose you bind a page to the AGP aperture, but don't change the kernel >> linear map caching policy. >> Then a speculatively prefetching processor may read the memory into its >> cache and then decide it doesn't >> want to use it, and actually write it back. >> Meanwhile the GPU may have changed the contents of the page and that >> change will be overwritten. Apparently there were big problems with AMD >> Athlons actually doing this. Linux people claiming it was an Athlon bug >> and AMD people claiming it was within specs. >> >> > > http://www.linuxjournal.com/files/linuxjournal.com/linuxjournal/articles/061/6148/6148s1.html > > Is what I believe you are talking about, I'll add something to the > comment mentioning this.. > > Yup. In the end I believe the "change_page_attr(), global_flush_tlb()" sequence was the final outcome of this, but as I understand it, with your new code we never write through the GTT, which makes the only possible problem overwrites of GPU written data.
/Thomas > Dave. > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
