Messages in this thread Patch in this message |  | | Subject | Re: [PATCH 02/49] x86/cpu: Describe hybrid CPUs in cpuinfo_x86 | From | "Liang, Kan" <> | Date | Mon, 8 Feb 2021 14:04:24 -0500 |
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On 2/8/2021 12:56 PM, Borislav Petkov wrote: > On Mon, Feb 08, 2021 at 07:24:59AM -0800, kan.liang@linux.intel.com wrote: >> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h >> index c20a52b..1f25ac9 100644 >> --- a/arch/x86/include/asm/processor.h >> +++ b/arch/x86/include/asm/processor.h >> @@ -139,6 +139,16 @@ struct cpuinfo_x86 { >> u32 microcode; >> /* Address space bits used by the cache internally */ >> u8 x86_cache_bits; >> + /* >> + * In hybrid processors, there is a CPU type and a native model ID. The >> + * CPU type (x86_cpu_type[31:24]) describes the type of micro- >> + * architecture families. The native model ID (x86_cpu_type[23:0]) >> + * describes a specific microarchitecture version. Combining both >> + * allows to uniquely identify a CPU. >> + * >> + * Please note that the native model ID is not related to x86_model. >> + */ >> + u32 x86_cpu_type; > > Why are you adding it here instead of simply using > X86_FEATURE_HYBRID_CPU at the call site? > > How many uses in this patchset? > > /me searches... > > Exactly one. > > Just query X86_FEATURE_HYBRID_CPU at the call site and read what you > need from CPUID and use it there - no need for this. >
I think it's good enough for perf, but I'm not sure whether other codes need the CPU type information.
Ricardo, do you know?
Maybe we should implement a generic function as below for this? (Not test. Just use as an example.)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index a66c1fd..679f5fe 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2056,3 +2056,11 @@ void arch_smt_update(void) /* Check whether IPI broadcasting can be enabled */ apic_smt_update(); } + +u32 x86_read_hybrid_type(void) +{ + if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) + return cpuid_eax(0x0000001a); + + return 0; +}
Thanks, Kan
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