x86/mpx: remove MPX from arch/x86

From: Dave Hansen <dave.hansen@linux.intel.com>

MPX is being removed from the kernel due to a lack of support
in the toolchain going forward (gcc).

This removes all the remaining (dead at this point) MPX handling
code remaining in the tree.  The only remaining code is the XSAVE
support for MPX state which is currently needd for KVM to handle
VMs which might use MPX.

Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>

arch/x86/include/asm/bugs.h

@@ -6,12 +6,6 @@
 
 extern void check_bugs(void);
 
-#if defined(CONFIG_CPU_SUP_INTEL)
-void check_mpx_erratum(struct cpuinfo_x86 *c);
-#else
-static inline void check_mpx_erratum(struct cpuinfo_x86 *c) {}
-#endif
-
 #if defined(CONFIG_CPU_SUP_INTEL) && defined(CONFIG_X86_32)
 int ppro_with_ram_bug(void);
 #else

arch/x86/include/asm/disabled-features.h

@@ -10,12 +10,6 @@
  * cpu_feature_enabled().
  */
 
-#ifdef CONFIG_X86_INTEL_MPX
-# define DISABLE_MPX	0
-#else
-# define DISABLE_MPX	(1<<(X86_FEATURE_MPX & 31))
-#endif
-
 #ifdef CONFIG_X86_SMAP
 # define DISABLE_SMAP	0
 #else
@@ -74,7 +68,7 @@
 #define DISABLED_MASK6	0
 #define DISABLED_MASK7	(DISABLE_PTI)
 #define DISABLED_MASK8	0
-#define DISABLED_MASK9	(DISABLE_MPX|DISABLE_SMAP)
+#define DISABLED_MASK9	(DISABLE_SMAP)
 #define DISABLED_MASK10	0
 #define DISABLED_MASK11	0
 #define DISABLED_MASK12	0

arch/x86/include/asm/mmu.h

@@ -50,10 +50,6 @@ typedef struct {
 	u16 pkey_allocation_map;
 	s16 execute_only_pkey;
 #endif
-#ifdef CONFIG_X86_INTEL_MPX
-	/* address of the bounds directory */
-	void __user *bd_addr;
-#endif
 } mm_context_t;
 
 #define INIT_MM_CONTEXT(mm)						\

arch/x86/include/asm/mmu_context.h

@@ -12,7 +12,6 @@
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include <asm/paravirt.h>
-#include <asm/mpx.h>
 #include <asm/debugreg.h>
 
 extern atomic64_t last_mm_ctx_id;
@@ -275,25 +274,6 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
 static inline void arch_unmap(struct mm_struct *mm, unsigned long start,
 			      unsigned long end)
 {
-	/*
-	 * mpx_notify_unmap() goes and reads a rarely-hot
-	 * cacheline in the mm_struct.  That can be expensive
-	 * enough to be seen in profiles.
-	 *
-	 * The mpx_notify_unmap() call and its contents have been
-	 * observed to affect munmap() performance on hardware
-	 * where MPX is not present.
-	 *
-	 * The unlikely() optimizes for the fast case: no MPX
-	 * in the CPU, or no MPX use in the process.  Even if
-	 * we get this wrong (in the unlikely event that MPX
-	 * is widely enabled on some system) the overhead of
-	 * MPX itself (reading bounds tables) is expected to
-	 * overwhelm the overhead of getting this unlikely()
-	 * consistently wrong.
-	 */
-	if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
-		mpx_notify_unmap(mm, start, end);
 }
 
 /*