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

Pull x86 pti fixes from Thomas Gleixner:
 "Two small updates for the speculative distractions:

   - Make it more clear to the compiler that array_index_mask_nospec()
     is not subject for optimizations. It's not perfect, but ...

   - Don't report XEN PV guests as vulnerable because their mitigation
     state depends on the hypervisor. Report unknown and refer to the
     hypervisor requirement"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/spectre_v1: Disable compiler optimizations over array_index_mask_nospec()
  x86/pti: Don't report XenPV as vulnerable

Author: torvalds

arch/x86/include/asm/barrier.h

@@ -38,7 +38,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
 {
 	unsigned long mask;
 
-	asm ("cmp %1,%2; sbb %0,%0;"
+	asm volatile ("cmp %1,%2; sbb %0,%0;"
 			:"=r" (mask)
 			:"g"(size),"r" (index)
 			:"cc");

arch/x86/kernel/cpu/bugs.c

@@ -27,6 +27,7 @@
 #include <asm/pgtable.h>
 #include <asm/set_memory.h>
 #include <asm/intel-family.h>
+#include <asm/hypervisor.h>
 
 static void __init spectre_v2_select_mitigation(void);
 static void __init ssb_select_mitigation(void);
@@ -664,6 +665,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		if (boot_cpu_has(X86_FEATURE_PTI))
 			return sprintf(buf, "Mitigation: PTI\n");
 
+		if (hypervisor_is_type(X86_HYPER_XEN_PV))
+			return sprintf(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n");
+
 		break;
 
 	case X86_BUG_SPECTRE_V1: