Re: [PATCH v2 8/8] x86/fpu/xstate: Restore supervisor xstates for __fpu__restore_sig()

Yu-cheng Yu
2020-02-28T16:41:05Z

On Fri, 2020-02-28 at 17:23 +0100, Borislav Petkov wrote:
> On Fri, Feb 28, 2020 at 07:53:38AM -0800, Yu-cheng Yu wrote:
> > Yes, saving only supervisor states is optimal, but doing XSAVES with a
> > partial RFBM changes xcomp_bv.
>
> ... and that means what exactly in plain english?

When XSAVES writes to an xsave buffer, xsave->header.xcomp_bv is set to
include only saved components, effectively changing the buffer's format.

I will include this in the comments.

Yu-cheng