Messages in this thread | | | From | "Michael S. Zick" <> | Subject | Re: [PATCH] X86: cpu_debug support for VIA / Centaur CPU's | Date | Wed, 10 Jun 2009 06:11:10 -0500 |
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On Wed June 10 2009, Ingo Molnar wrote: > > * H. Peter Anvin <hpa@kernel.org> wrote: > > > Ingo Molnar wrote: > > > > > > MSRs should really be enumerated along CPU features. They will be > > > accessed if a CPU offers that CPU feature. > > > > > > > Nice in theory, but so many MSRs have to be enumerated with obscure test > > combinations, that it really isn't practical in the general case. That > > is why we have the safe MSR variants. > > > > > > > > Yeah, the safe read should never fault - there should be all > > > zeroes or an error return. > > > > > > > Error return, MSRs #GP if not present. All zero means a present > > MSR (which is zero.) > > yes, of course - i meant the /debug/x86/cpu/* behavior: it should > either result zeroes, or should return -EINVAL. (probably the > latter) >
Return zeroes - same as hardware case for bits which can't be set. Returning -EINVAL might match a specific bit pattern caller is looking for.
Mike > Ingo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > >
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