x86: reduce CONFIG_X86_PPRO_FENCE bloat

[firefly-linux-kernel-4.4.55.git] / arch / x86 / Kconfig.cpu

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 018d68e3184e029b4ad85d771a6bf308cd7f9799..e09a6b73a1aab5c3fc6a353e22af4936b047416f 100644 (file)
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -321,8 +321,17 @@ config X86_XADD
        depends on X86_32 && !M386
 
 config X86_PPRO_FENCE
-       def_bool y
+       bool "PentiumPro memory ordering errata workaround"
        depends on M686 || M586MMX || M586TSC || M586 || M486 || M386 || MGEODEGX1
+       help
+         Old PentiumPro multiprocessor systems had errata that could cause memory
+         operations to violate the x86 ordering standard in rare cases. Enabling this
+         option will attempt to work around some (but not all) occurances of
+         this problem, at the cost of much heavier spinlock and memory barrier
+         operations.
+
+         If unsure, say n here. Even distro kernels should think twice before enabling
+         this: there are few systems, and an unlikely bug.
 
 config X86_F00F_BUG
        def_bool y