RFC Pile o' entry stack changes

Hi all-

Here's a pile of entry changes. In brief summary:

- Lots of people (Linus included) have asked to convert the entry code to pop registers on exit instead of movqing them off the stack. This makes a bunch of progress in that direction.

- Linux's sp0 handling has annoyed me for a while. We have thread_struct::sp0, which never made much sense to me. This series removes it on x86_64 and removes most references on x86_32.

- Xen PV's cpuinit code did incomprehensible things with stack pointers. This makes it comprehensible.

Juergen, this needs a bit of help on Xen -- see the NMI patch for details.

Reviews would be appreciated :)

Andy Lutomirski (17):
x86/asm/64: Remove the restore_c_regs_and_iret label x86/asm/64: Split the iret-to-user and iret-to-kernel paths x86/asm/64: Move SWAPGS into the common iret-to-usermode path x86/asm/64: Simplify reg restore code in the standard IRET paths x86/asm/64: Shrink paranoid_exit_restore and make labels local x86/asm/64: Use pop instead of movq in syscall_return_via_sysret x86/asm/64: Merge the fast and slow SYSRET paths x86/asm/64: De-Xen-ify our NMI code
x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of

    native_load_sp0()

x86/asm/64: Pass sp0 directly to load_sp0()
x86/asm: Add task_top_of_stack() to find the top of a task's stack x86/xen/64: Clean up SP code in cpu_initialize_context() x86/boot/64: Stop initializing TSS.sp0 at boot
x86/asm/64: Remove all remaining direct thread_struct::sp0 reads x86/boot/32: Fix cpu_current_top_of_stack initialization at boot x86/asm/64: Remove thread_struct::sp0
x86/traps: Use a new on_thread_stack() helper to clean up an assertion

 arch/x86/entry/calling.h              |   9 +++
 arch/x86/entry/entry_64.S             | 133 ++++++++++++++++++----------------
 arch/x86/entry/entry_64_compat.S      |   3 +-
 arch/x86/include/asm/compat.h         |   1 +
 arch/x86/include/asm/paravirt.h       |   5 +-
 arch/x86/include/asm/paravirt_types.h |   2 +-
 arch/x86/include/asm/processor.h      |  68 +++++++++--------
 arch/x86/include/asm/switch_to.h      |  23 ++++++
 arch/x86/include/asm/thread_info.h    |  11 ---
 arch/x86/kernel/cpu/common.c          |  12 ++-
 arch/x86/kernel/head_64.S             |   2 +-
 arch/x86/kernel/process.c             |   3 +-
 arch/x86/kernel/process_32.c          |   3 +-
 arch/x86/kernel/process_64.c          |   5 +-
 arch/x86/kernel/smpboot.c             |   3 +-
 arch/x86/kernel/traps.c               |   3 +-
 arch/x86/kernel/vm86_32.c             |  14 ++--
 arch/x86/lguest/boot.c                |   7 +-
 arch/x86/xen/enlighten_pv.c           |   7 +-
 arch/x86/xen/smp_pv.c                 |  17 ++++-
 20 files changed, 192 insertions(+), 139 deletions(-)

2.13.5