On 11/30/20 10:06 AM, Yu, Yu-cheng wrote:
>>> + if (!boot_cpu_has(X86_FEATURE_SHSTK) &&
>>> + !boot_cpu_has(X86_FEATURE_IBT))
>>> + xfeatures_mask_all &= ~BIT_ULL(i);
>>> + } else {
>>> + if ((xsave_cpuid_features[i] == -1) ||
>>
>> Where did the -1 come from? Was that introduced earlier in this series?
>> I don't see any way a xsave_cpuid_features[] can be -1 in the
>> current tree.
>
> Yes, we used to have a hole in xsave_cpuid_features[] and put -1 there.
> Do we want to keep this in case we again have holes in the future?
So, it's dead code for the moment and it's impossible to tell what -1
means without looking at git history? That seems, um, suboptimal.
Shouldn't we have:
#define XFEATURE_NO_DEP -1
?
And then this code becomes:
if ((xsave_cpuid_features[i] == XFEATURE_NO_DEP))
// skip it...
We can even put a comment in xsave_cpuid_features[] to tell folks to use
it.
