Re: [GIT PULL] Intel IOMMU for 4.1

[Linda Knippers <linda.knippers-VXdhtT5mjnY@public.gmane.org>]

On 4/27/2015 11:48 AM, Linus Torvalds wrote:
> On Mon, Apr 27, 2015 at 8:39 AM, Alex Williamson
> <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>>
>> Since this got pulled anyway, do you plan to follow-up with patches to
>> limit the graphics RMRR exception to the known and acceptable uses and
>> document them, or should I send a revert patch?  I don't think what we
>> have here is acceptable going forward or being backported to stable.
>> Thanks,
> 
> Does anybody actually *care* about RMRR?

I care, just not so much for GPUs.

> The thing is shit. We know it's shit. We already had Linda pipe up to
> tell us that there are bogus RMRR's for ever slot in older machines.

I'd call them unnecessary.

> And we already ignore RMRR for USB controllers because it was just
> useless garbage.
> 
> Is there any reason to *not* just ignore RMRR for all video devices
> like we do now? Seriously?

I was only speaking about one particular use case of RMRR for video
devices.  I'm not sure what anyone else is doing with them.

> I'm *so* not impressed with firmware tables. These things are always
> uniformly wrong. We should strive to generate the information from our
> actual hardware knowledge, with BIOS tables being the absolutely least
> trusted source of information.

In some cases though, you really do need the firmware to provide the tables.
Too few RMRRs are worse than too many.

-- ljk
> 
>                      Linus
>