Hi Ben,
On Mon, Oct 16, 2017 at 06:34:52PM +0100, Ben Hutchings wrote:
> On Mon, 2017-10-02 at 20:59 +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> [...]
> > From: Eric Biggers <ebiggers@xxxxxxxxxx>
> >
> > commit 814fb7bb7db5433757d76f4c4502c96fc53b0b5e upstream.
> >
> > [Please apply to 4.4-stable. Note: the backport includes the
> > fpstate_init() call in xstateregs_set(), since fix is useless without
> > it. It was added by commit 91c3dba7dbc1 ("x86/fpu/xstate: Fix PTRACE
> > frames for XSAVES"), but it doesn't make sense to backport that whole
> > commit.]
> [...]
>
> Why doesn't it make sense to backport that? It seems less important
> than this fix, but it fixes a userspace-visible regression.
>
It seems that commit was part of a series of commits that fixed XSAVES support
and then re-enabled it. Before then the XSAVES support was actually disabled;
see commit e88221c50cad ("x86/fpu: Disable XSAVES* support for now"). So commit
91c3dba7dbc1 didn't fix a regression, as the code was already disabled.
Eric