On Tue, Jun 17, 2014 at 9:04 AM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > On Mon, 2014-06-16 at 23:35 -0600, Alex Williamson wrote: >> >> Any idea what an off-the-shelf Asus motherboard would be doing with an >> RMRR on the Intel HD graphics? >> >> dmar: RMRR base: 0x000000bb800000 end: 0x000000bf9fffff >> IOMMU: Setting identity map for device 0000:00:02.0 [0xbb800000 - 0xbf9fffff] > > Hm, we should have thought of that sooner. That's quite normal — it's > for the 'stolen' memory used for the framebuffer. And maybe also the > GTT, and shadow GTT and other things; I forget precisely what, and it > varies from one setup to another. > > I'd expect fairly much all systems to have an RMRR for the integrated > graphics device if they have one, and your patch¹ is going to prevent > assignment of those to guests... as you've presumably noticed. > > I'm not sure if the i915 driver is capable of fully reprogramming the > hardware to completely stop using that region, to allow assignment to a > guest with a 'pure' memory map and no stolen region. I suppose it must, > if assignment to guests was working correctly before? > > Perhaps the better answer here is not to have the special cases in > 'device_is_rmrr_locked()', and instead allow a device driver to call a > 'iommu_release_rmrrs()' function once it's reset the hardware to *stop* > doing whatever DMA the BIOS set it up with. We've always been struggling with stolen handling, and we've' always been struggling with vt-d stuff. Also pass-through seems to be a major pain (I've never tried myself). Given all that I'm voting for keeping the RMRR and everything else as much like for the normal case since I have no idea what exactly must be remapped and what's optional. The gpu is definitely keeping a lot of it's own private stuff in various chunks of stolen memory. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
