Re: [Intel-gfx] [PATCH] iommu: export no_iommu and dmar_disabled symbols

On Wed, 23 Nov 2011 20:36:00 +0000, David Woodhouse dwmw2@infradead.org wrote:

This is horrid. In the general case, drivers have no business knowing this. We need to properly identify what is wrong with this hardware, and put in a quirk for it — perhaps refusing to enable the IOMMU at all on the broken chipsets.

That'd be fine with me, right now we're disabling RC6 and semaphores -- semaphores aren't all that important, although they do improve performance a bit. RC6 is important, saving a huge amount of power.

I'd also be OK with requiring special options to enable DMAR and having that also disable RC6/semaphores, if you'd rather expose that. In either case, we need something that works and avoids hanging machines.