I just realized there is yet another oddity in this code:
> @@ -78,8 +69,10 @@ struct cpuid_parameters_t {
> struct feature_entry {
> enum rte_cpu_flag_t feature; /**< feature name */
The structure contains a field with an enum value...
> char name[CPU_FLAG_NAME_MAX_LEN]; /**< String for printing */
> - struct cpuid_parameters_t params; /**< cpuid parameters */
> - uint32_t feature_mask; /**< bitmask for feature */
> + uint32_t leaf; /**< cpuid leaf */
> + uint32_t subleaf; /**< cpuid subleaf */
> + uint32_t reg; /**< cpuid register */
> + uint32_t bit; /**< cpuid register bit */
> };
>
>
> /*
> @@ -240,17 +207,20 @@ rte_cpu_get_features(struct cpuid_parameters_t params)
> int
> rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
> {
> - int value;
> + const struct feature_entry *feat;
> + cpu_registers_t regs;
>
> if (feature >= RTE_CPUFLAG_NUMFLAGS)
> /* Flag does not match anything in the feature tables */
> return -ENOENT;
>
> - /* get value of the register containing the desired feature */
> - value = rte_cpu_get_features(cpu_feature_table[feature].params);
> + feat = &cpu_feature_table[feature];
> +
> + /* get the cpuid leaf containing the desired feature */
> + rte_cpu_get_features(feat->leaf, feat->subleaf, ®s);
>
> /* check if the feature is enabled */
> - return (cpu_feature_table[feature].feature_mask & value) > 0;
> + return (regs[feat->reg] >> feat->bit) & 1;
> }
>
> /**
... however, this field is never actually accessed *anywhere* in the
code; the code instead uses the enum value as the table index. There is
absolutely no enforcement that the table contents is aligned with the enum.
If C99-style initializers are permitted in this codebase, I would
strongly recommend using them, and then drop the enum field in struct
feature_entry and use a macro such as:
#define FEAT(name,leaf,subleaf,reg,bit) \
[RTE_CPUFLAG_##f] = { leaf, subleaf, reg, bit, #f },
(I'd move the string to the end, but that is just a microoptimization.
I'm kind of OCD that way.)
-hpa
