Messages in this thread | | | Date | Wed, 10 Jun 2009 19:42:23 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH -tip] x86: cpu/proc.c adding extended_cpuid_level for /proc/cpuinfo |
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On Wed, Jun 10, 2009 at 10:14:09AM -0700, H. Peter Anvin wrote: > >>>> > >>> The more I'm thinking about this I think it was a mistake to put cpuid > >>> level: there in the first place, too. My opinion is increasingly to > >>> leave this to x86info or other user-space tools. > >>> > >> cpuid level is as important as cpu family, model and stepping. > >> > >> For Intel, in some cases cpuid level is more important then cpu family, > >> model and stepping. Like you cannot tell by looking at cpu family, model > >> and stepping which model is new and which is old like 05_01 or 06_1A or > >> 0F_03H ? > >> > >> But by looking at cpuid level and extended cpuid level you can tell > >> which is new and which is old and which supports more features. > >> > >> So cpuid level and extended cpuid level is better scale than cpu family, > >> model and stepping. So I think hiding this valuable information is a > >> crime. > > > > cpuid level and extended cpuid level tells the information about Intel > > processor model. Do you still think it is useless and should not be present > > in /proc/cpuinfo . > > > > I think it's pointless, because if you're doing this kind of stuff you > might as well talk to CPUID directly. We have a CPUID interface > already. The kernel isn't meant to replicate x86info or any of those > tools -- it really can't, and at that point why stop at x86info... we > could replicate arbitrary applications at that point. > > As far as extended CPUID, why only the 0x0000 and 0x8000 ranges? > Transmeta used 0x8086 and VIA uses 0xC000, but we don't even cache those > internally, nevermind display them. > > I'm not really all that doctrinal about this, but I'd like to get a > decent answer to the question "where does it stop, *and why*". It's a > slippery slope, and without a target, it goes on forever.
I still fail to see a real use case which requires adding that info to the kernel and querying CPUID directly is _absolutely_ not an option. This is what the decisive argument should be and not some "but we have already this and that in there." Otherwise its like painting a broken car pink - it's still broken.
-- Regards/Gruss, Boris.
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