The function copy_kernel_to_xregs_err() uses XRSTOR which can work with
standard or compacted format without supervisor xstates. However, when
supervisor xstates are present, XRSTORS must be used. Fix it by using
XRSTORS when supervisor state handling is enabled.

I also considered if there were additional cases where XRSTOR might be
mistakenly called instead of XRSTORS.  There are only three XRSTOR sites
in the kernel:

1. copy_kernel_to_xregs_booting(), already switches between XRSTOR and
   XRSTORS based on X86_FEATURE_XSAVES.

2. copy_user_to_xregs(), which *needs* XRSTOR because it is copying from
   userspace and must never copy supervisor state with XRSTORS.

3. copy_kernel_to_xregs_err() mistakenly used XRSTOR only.  Fix it.

 [ bp: Massage commit message. ]
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20200512145444.15483-8-yu-cheng.yu@intel.com