Messages in this thread | | | Date | Thu, 08 May 2008 15:39:47 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] x86: introduce a new Linux defined feature flag for PAT support |
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Rene Herman wrote: > On 08-05-08 12:19, Andi Kleen wrote: > >>> Use a new Linux defined X86_FEATURE_PAT_GOOD feature flag to >> >> Better would be PAT_TESTED or PAT_RANDOMLY_APPROVED. Most of these >> CPUs without PAT_GOOD have actually perfectly good PAT, as Windows >> proves every day. >> >> The main flaw in all of this of course is that there is no procedure >> to test CPUs which do not have the flag set yet. > > Quite. And hiding the fact that the CPU _should_ have perfectly good > PAT doesn't help any at all. The discussion turned into a mini-flame > war enough that now noone would even consider backing down, but this > current PAT setup just sucks plain and simple.
For old CPUs it is actually ok (after all they worked for years without PAT), I just don't like it for new CPUs. It's a bad idea there and in the x86 world it is a reasonable expectation that CPU features generally work.
That said I am not aware of that many PAT erratas even on old CPUs. There are a few, but they are known and well understood and could well be black listed.
-Andi
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