[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] x86/Intel: don't log bogus frequency range on Core/Core2 processors
On 08.02.2022 09:54, Roger Pau Monné wrote: > On Fri, Feb 04, 2022 at 02:56:43PM +0100, Jan Beulich wrote: >> Models 0F and 17 don't have PLATFORM_INFO documented. While it exists on >> at least model 0F, the information there doesn't match the scheme used >> on newer models (I'm observing a range of 700 ... 600 MHz reported on a >> Xeon E5345). > > Maybe it would be best to limit ourselves to the models that have the > MSR documented in the SDM? Well, yes, that's what I wasn't sure about: The information is used only for logging, so it's not the end of the world if we display something strange. We'd want to address such anomalies (like the one I did observe here) of course. But I wonder whether being entirely silent is really better. >> --- a/xen/arch/x86/cpu/intel.c >> +++ b/xen/arch/x86/cpu/intel.c >> @@ -435,6 +435,26 @@ static void intel_log_freq(const struct >> if ( c->x86 == 6 ) >> switch ( c->x86_model ) >> { >> + static const unsigned short core_factors[] = >> + { 26667, 13333, 20000, 16667, 33333, 10000, 40000 }; >> + >> + case 0x0e: /* Core */ >> + case 0x0f: case 0x16: case 0x17: case 0x1d: /* Core2 */ >> + /* >> + * PLATFORM_INFO, while not documented for these, appears to >> + * exist in at least some cases, but what it holds doesn't >> + * match the scheme used by newer CPUs. At a guess, the min >> + * and max fields look to be reversed, while the scaling >> + * factor is encoded in FSB_FREQ. >> + */ >> + if ( min_ratio > max_ratio ) >> + SWAP(min_ratio, max_ratio); >> + if ( rdmsr_safe(MSR_FSB_FREQ, msrval) || >> + (msrval &= 7) >= ARRAY_SIZE(core_factors) ) >> + return; >> + factor = core_factors[msrval]; >> + break; >> + >> case 0x1a: case 0x1e: case 0x1f: case 0x2e: /* Nehalem */ >> case 0x25: case 0x2c: case 0x2f: /* Westmere */ >> factor = 13333; > > Seeing that the MSR is present on non documented models and has > unknown behavior we might want to further sanity check that min < max > before printing anything? But I'm already swapping the two in the opposite case? Jan
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