-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Keith Packard wrote: > On Tue, 2005-08-23 at 16:22 +0200, Stephane Marchesin wrote: > >>Ok, here is what came out of the irc meeting : >>- we don't need to enforce video memory ownership, but the drm needs to >>be able to track allocation owners anyway, for example if a process dies >>unexpectedly. > > How expensive would it be to protect one processes video memory from > another? I would like to be able to run applications for different users > on the screen at the same time and prevent both reading and writing of > the images. If not possible on current hardware, what would it take from > new hardware to make this possible?
You'd need the same stuff that you need to protect system memory. You'd need a hardware MMU that could block the accesses. It might be possible to do it in software by looking at the command stream, but I suspect that would be pretty expensive. It would be worth a try, I suppose. >>- regions that are marked as "preserve" have a matching backing store >>region in system ram. That region is made of pinned pages. > > Do they really need to be pinned? That's a huge waste of memory. We had this discussion too. The problem is you need the memory allocated in advance to avoid the allocation failures when the kernel needs to back up the data. If the memory isn't pinned, it can get paged out, and, apparently, the kernel can page-in user pages in the way that we want. Dave Airlie made some comments about that, but I don't remember exactly what he said. Ideally, we want to reserve some pages, but we don't care about their contents. When the kernel needs to back the data, it just needs to get a bunch of blank pages. Dave also mentioned that there were some "dirty kernel tricks" that would allow that, but that it might not be portable (to BSD) or even stable across Linux kernel versions. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (GNU/Linux) iD8DBQFDC1YsX1gOwKyEAw8RAvqkAJ9qfMowGZ6e1B0ejRJaLX3X9gKRrACeNim7 oUZia1N544Mzvx/sLx2mtNs= =G8iT -----END PGP SIGNATURE----- ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
