Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit_lock if possible

Ingo Molnar
2011-03-25T19:32:28Z

* Robert Richter <robert.richter@amd.com> wrote:

> > Its all a big clusterfuck and really the best way (IMO) is what we have
> > now to put pressure on and force the BIOS vendors to play nice.
> >
> > I assume both HP and DELL will be seriously unhappy with the kernel
> > spewing FIRMWARE BUG messages on boot on their boxen, the question is,
> > will they be unhappy enough to fix it..
>
> So, we better stick then with option 1. My experience is that new
> system's bioses try not to claim perfctrs (affected systems I have
> seen are about 2-3 years old), but I am not really sure here.

That's good news - BIOSen unilaterally stealing PMU real estate is a really
utterly crazy concept.

For a limited physical resource like the PMU the correct approach to add
PMU-using features is to add an OS driver that implements the feature via the
regular PMU access functions. We already have such features so it's very much
possible. That way it all becomes controllable and configurable to the user.

Thanks,

Ingo