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.
>
> If a caller tries to pass a non-enabled xfeature in, we appear to just
> silently drop it and return success. Is that really what we want to do
> or do we want to error out?
Let it fail. I will chage it.
