On 03/25/2014 10:03 AM, Neil Horman wrote:
> int
> rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
> {
> - int value;
> + const struct feature_entry *feat;
> + cpuid_registers_t regs;
> + static uint32_t max_leaf = 0;
> +
> + if (!max_leaf) {
> + /* Get the max input leaf for this processor */
> + rte_cpu_get_features(0, 0, regs);
> + max_leaf = regs[REG_EAX];
> + }
>
> 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];
> +
> + if (!feat->leaf)
> + /* This entry in the table wasn't filled out! */
> + return -EFAULT;
> + if (feat->leaf > max_leaf)
> + return -EINVAL;
This doesn't quite work. The max_leaf is per CPUID "group", i.e. the
8000xxxx CPUID leaves have a different limit than 0000xxxx leaves. So I
would just do this as:
rte_cpu_get_features(feat->leaf & 0xffff0000, 0, regs);
if (((regs[REG_EAX] ^ feat->leaf) & 0xffff0000) ||
regs[REG_EAX] < feat->leaf)
return 0;
Returning 0 is the right thing, because this is a legitimate instance of
"this feature is not supported."
The first part is a sanity check that the CPUID leaf group is supported
at all; the second part is the actual limit check.
-hpa
