On 04/29/2016 03:30 PM, Yu-cheng Yu wrote:
> On Fri, Apr 29, 2016 at 01:25:34PM -0700, Dave Hansen wrote:
>> On 03/04/2016 10:12 AM, Yu-cheng Yu wrote:
>>> + for (i = 0; i < XFEATURE_MAX; i++) {
>>> + /*
>>> + * Copy only in-use xstates.
>>> + */
>>> + if (((header.xfeatures >> i) & 1) && xfeature_enabled(i)) {
>>> + void *src = get_xsave_addr_no_check(xsave, i);
>>
>> How could a bit in header.xfeatures get set if it is not set in
>> xfeature_enabled() aka xfeatures_mask aka XCR0?
>
> Do you mean, we should test xfeature_enabled(i) first, like,
>
> if (xfeature_enabled(i) && ((header.xfeatures >> i) & 1)) ?
>
> The result will be the same, like you said, if XCR0[i] is not set,
> hader.xfeatures[i] cannot be set. But if XCR0[i] is set,
> header.xfeatures[i] can be cleared.
I think the xfeature_enabled(i) is probably redundant. Does it serve
any actual purpose?
