[Intel-gfx] [PATCH v2 for -fixes] drm/i915: Disable stolen memory when DMAR is active

[David Woodhouse]

On Thu, 2014-03-20 at 09:36 +0200, Jani Nikula wrote:
> 
> Or an additional knob, in case it's really not working and people want
> to get other things depending on prelim hw support done.

Yeah. Perhaps the best answer is a 'disable_silicon_workarounds' option,
to disable *all* workarounds for silicon bugs. Couple that with a printk
telling the user that workarounds are disabled *and* VT-d is enabled.

That's a nice simple thing for the chipset validation folks to be
looking for. Unless they see that and have no issues with either
framebuffer or X, the chipset hasn't been tested.

That aside, I'm also unhappy with your patch on general principles. As a
rule I'd like to see references to a *specific* published erratum, for
anything we disable. Otherwise we're just admitting that life is too
hard and we *never* bother to test our silicon before we ship it and we
*expect* it to be broken.

If we chase broken hardware to the point where errata are published, we
should hopefully ensure that the problem feeds back to the validation
folks who haven't done their job properly. Every time.

(Pondered making this an internal email, but hey — *you're* the one who
said "our hardware is always broken and we don't even bother to track
individual brokenness". I'm just translating it into English from what's
in your patch :)

-- 
dwmw2

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