Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES area

From: Ingo Molnar
Date: Tue Jan 24 2017 - 03:08:37 EST

* Kevin Hao <haokexin@xxxxxxxxx> wrote:

> > other than helping to hide bugs?
> Why do you think it hide the bug? In contrast, I think my patch fixes what the
> bug really is. The memory area we fake up is bug, we should fix it there.

The intention is to have a single FPU format set at bootup and xcomp_bv is
essentially an invariant (constant) inherited by all tasks from early boot. In
that sense setting xsave.header.xcomp_bv in copyin_to_xsaves() is misplaced.

So I combined the two commits: I kept your original fix but applied Yu-cheng Yu's
patch that moves the initialization from copyin_to_xsaves() to fpstate_init().