Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

Merge branch 'x86-fpu-for-linus' of git://git./linux/kernel/git/tip/tip

Pull x86 fpu fixes and cleanups from Ingo Molnar:
 "This is _way_ more cleanups than fixes, but the bugs were subtle and
  hard to hit, and the primary reason for them existing was the
  unnecessary historical complexity of some of the x86/fpu interfaces.

  The first bunch of commits clean up and simplify the xstate user copy
  handling functions, in reaction to the collective head-scratching
  about the xstate user-copy handling code that leads up to the fix for
  this SkyLake xstate handling bug:

     0852b374173b: x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on Intel Skylake CPUs

  The cleanups don't change any functionality, they just (hopefully)
  make it all clearer, more consistent, more debuggable and more robust.

  Note that most of the linecount increase comes from these commits,
  where we better split the user/kernel copy logic by having more
  variants, instead repeated fragile patterns of:

               if (kbuf) {
                       memcpy(kbuf + pos, data, copy);
               } else {
                       if (__copy_to_user(ubuf + pos, data, copy))
                               return -EFAULT;
               }

  The next bunch of commits simplify the FPU state-machine to get rid of
  old lazy-FPU idiosyncrasies - a defensive simplification to make all
  the code easier to review and fix. No change in functionality.

  Then there's a couple of additional debugging tweaks: static checker
  warning fix and move an FPU related warning to under WARN_ON_FPU(),
  followed by another bunch of commits that represent a finegrained
  split-up of the fixes from Eric Biggers to handle weird xstate bits
  properly.

  I did this finegrained split-up because some of these fixes also
  impact the ABI for weird xstate handling, for which we'd like to have
  good bisection results, should they cause any problems. (We also had
  one regression with the more monolithic fixes, so splitting it all up
  sounded prudent for robustness reasons as well.)

  About the whole series: the commits up to 03eaec81ac09 have been in
  -next for months - but I've recently rebased them to remove a state
  machine clean-up commit that was objected to, and to make it more
  bisectable - so technically it's a new, rebased tree.

  Robustness history: this series had some regressions along the way,
  and all reported regressions have been fixed. All but one of the
  regressions manifested itself as easy to report warnings. The previous
  version of this latest series was also in linux-next, with one
  (warning-only) regression reported which is fixed in the latest
  version.

  Barring last minute brown paper bag bugs (and the commits are now
  older by a day which I'd hope helps paperbag reduction), I'm
  reasonably confident about its general robustness.

  Famous last words ..."

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (42 commits)
  x86/fpu: Use using_compacted_format() instead of open coded X86_FEATURE_XSAVES
  x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_user_to_xstate()
  x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate()
  x86/fpu: Copy the full header in copy_user_to_xstate()
  x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_kernel_to_xstate()
  x86/fpu: Eliminate the 'xfeatures' local variable in copy_kernel_to_xstate()
  x86/fpu: Copy the full state_header in copy_kernel_to_xstate()
  x86/fpu: Use validate_xstate_header() to validate the xstate_header in __fpu__restore_sig()
  x86/fpu: Use validate_xstate_header() to validate the xstate_header in xstateregs_set()
  x86/fpu: Introduce validate_xstate_header()
  x86/fpu: Rename fpu__activate_fpstate_read/write() to fpu__prepare_[read|write]()
  x86/fpu: Rename fpu__activate_curr() to fpu__initialize()
  x86/fpu: Simplify and speed up fpu__copy()
  x86/fpu: Fix stale comments about lazy FPU logic
  x86/fpu: Rename fpu::fpstate_active to fpu::initialized
  x86/fpu: Remove fpu__current_fpstate_write_begin/end()
  x86/fpu: Fix fpu__activate_fpstate_read() and update comments
  x86/fpu: Reinitialize FPU registers if restoring FPU state fails
  x86/fpu: Don't let userspace set bogus xcomp_bv
  x86/fpu: Turn WARN_ON() in context switch into WARN_ON_FPU()
  ...