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

Pull x86 CPU feature updates from Thomas Gleixner:
 "Updates for x86 CPU features:

   - Support for UMWAIT/UMONITOR, which allows to use MWAIT and MONITOR
     instructions in user space to save power e.g. in HPC workloads
     which spin wait on synchronization points.

     The maximum time a MWAIT can halt in userspace is controlled by the
     kernel and can be adjusted by the sysadmin.

   - Speed up the MTRR handling code on CPUs which support cache
     self-snooping correctly.

     On those CPUs the wbinvd() invocations can be omitted which speeds
     up the MTRR setup by a factor of 50.

   - Support for the new x86 vendor Zhaoxin who develops processors
     based on the VIA Centaur technology.

   - Prevent 'cat /proc/cpuinfo' from affecting isolated NOHZ_FULL CPUs
     by sending IPIs to retrieve the CPU frequency and use the cached
     values instead.

   - The addition and late revert of the FSGSBASE support. The revert
     was required as it turned out that the code still has hard to
     diagnose issues. Yet another engineering trainwreck...

   - Small fixes, cleanups, improvements and the usual new Intel CPU
     family/model addons"

* 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits)
  x86/fsgsbase: Revert FSGSBASE support
  selftests/x86/fsgsbase: Fix some test case bugs
  x86/entry/64: Fix and clean up paranoid_exit
  x86/entry/64: Don't compile ignore_sysret if 32-bit emulation is enabled
  selftests/x86: Test SYSCALL and SYSENTER manually with TF set
  x86/mtrr: Skip cache flushes on CPUs with cache self-snooping
  x86/cpu/intel: Clear cache self-snoop capability in CPUs with known errata
  Documentation/ABI: Document umwait control sysfs interfaces
  x86/umwait: Add sysfs interface to control umwait maximum time
  x86/umwait: Add sysfs interface to control umwait C0.2 state
  x86/umwait: Initialize umwait control values
  x86/cpufeatures: Enumerate user wait instructions
  x86/cpu: Disable frequency requests via aperfmperf IPI for nohz_full CPUs
  x86/acpi/cstate: Add Zhaoxin processors support for cache flush policy in C3
  ACPI, x86: Add Zhaoxin processors support for NONSTOP TSC
  x86/cpu: Create Zhaoxin processors architecture support file
  x86/cpu: Split Tremont based Atoms from the rest
  Documentation/x86/64: Add documentation for GS/FS addressing mode
  x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2
  x86/cpu: Enable FSGSBASE on 64bit by default and add a chicken bit
  ...

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 8dbca86c249b..15f0749d0a15 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1692,11 +1692,17 @@ nmi_restore:
 	iretq
 END(nmi)
 
+#ifndef CONFIG_IA32_EMULATION
+/*
+ * This handles SYSCALL from 32-bit code.  There is no way to program
+ * MSRs to fully disable 32-bit SYSCALL.
+ */
 ENTRY(ignore_sysret)
 	UNWIND_HINT_EMPTY
 	mov	$-ENOSYS, %eax
 	sysret
 END(ignore_sysret)
+#endif
 
 ENTRY(rewind_stack_do_exit)
 	UNWIND_HINT_FUNC