Messages in this thread | | | From | gengdongjiu <> | Subject | [question] extract the feature bits width to 4 | Date | Tue, 28 Nov 2017 19:17:40 +0800 |
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Hi,suzuki/mark,
very sorry to disturb you, I have a question that want to consult with you. For the CPU feature detection, why we use extract 4 bits width for the feature match instead of the actual bits number[1]? may be the actual hardware feature bit more than 4 bits. thanks!
static inline int __attribute_const__ cpuid_feature_extract_field(u64 features, int field, bool sign) { return cpuid_feature_extract_field_width(features, field, 4, sign); }
static bool feature_matches(u64 reg, const struct arm64_cpu_capabilities *entry) { int val = cpuid_feature_extract_field(reg, entry->field_pos, entry->sign);
return val >= entry->min_field_value; }
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