Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86: Fix performance regression caused by paravirt_ops on native kernels
  xen: use header for EXPORT_SYMBOL_GPL
  x86, 32-bit: fix kernel_trap_sp()
  x86: fix percpu_{to,from}_op()
  x86: mtrr: Fix high_width computation when phys-addr is >= 44bit
  x86: Fix false positive section mismatch warnings in the apic code

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index df9e885eee14..a6efe0a2e9ae 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -498,6 +498,19 @@ config PARAVIRT
           over full virtualization.  However, when run without a hypervisor
           the kernel is theoretically slower and slightly larger.
 
+config PARAVIRT_SPINLOCKS
+        bool "Paravirtualization layer for spinlocks"
+        depends on PARAVIRT && SMP && EXPERIMENTAL
+        ---help---
+          Paravirtualized spinlocks allow a pvops backend to replace the
+          spinlock implementation with something virtualization-friendly
+          (for example, block the virtual CPU rather than spinning).
+
+          Unfortunately the downside is an up to 5% performance hit on
+          native kernels, with various workloads.
+
+          If you are unsure how to answer this question, answer N.
+
 config PARAVIRT_CLOCK
         bool
         default n