Re: [PATCH v1 2/3] x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs
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From: Dave Hansen <hidden>
Date: 2021-01-07 15:53:50
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On 1/6/21 10:19 PM, Tony W Wang-oc wrote:
quoted hunk ↗ jump to hunk
+ /* + * These CPUs declare support SSE4.2 instruction sets but + * having low performance CRC32C instruction implementation. + */ + if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b)) + set_cpu_cap(c, X86_FEATURE_CRC32C); }
On the Intel side, we've tried to move away from open-coded model numbers. Say another CPU is released that has a microarchitecture close to 0x3b, but has a model of 0x3c. It's a *LOT* easier to grep for INTEL_FAM6_NEHALEM (or whatever) than 0x3c. See: arch/x86/include/asm/intel-family.h for examples.