Merge branch 'x86/asm' into x86/atomic

Merge reason:
	Conflict between LOCK_PREFIX_HERE and relative alternatives
	pointers

Resolved Conflicts:
	arch/x86/include/asm/alternative.h
	arch/x86/kernel/alternative.c

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
index de6cefb329dd..a0b3cac0547c 100644
--- a/arch/arm/include/asm/mmu_context.h
+++ b/arch/arm/include/asm/mmu_context.h
@@ -43,12 +43,23 @@ void __check_kvm_seq(struct mm_struct *mm);
 #define ASID_FIRST_VERSION	(1 << ASID_BITS)
 
 extern unsigned int cpu_last_asid;
+#ifdef CONFIG_SMP
+DECLARE_PER_CPU(struct mm_struct *, current_mm);
+#endif
 
 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
 void __new_context(struct mm_struct *mm);
 
 static inline void check_context(struct mm_struct *mm)
 {
+	/*
+	 * This code is executed with interrupts enabled. Therefore,
+	 * mm->context.id cannot be updated to the latest ASID version
+	 * on a different CPU (and condition below not triggered)
+	 * without first getting an IPI to reset the context. The
+	 * alternative is to take a read_lock on mm->context.id_lock
+	 * (after changing its type to rwlock_t).
+	 */
 	if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
 		__new_context(mm);
 
@@ -108,6 +119,10 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 		__flush_icache_all();
 #endif
 	if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) {
+#ifdef CONFIG_SMP
+		struct mm_struct **crt_mm = &per_cpu(current_mm, cpu);
+		*crt_mm = next;
+#endif
 		check_context(next);
 		cpu_switch_mm(next->pgd, next);
 		if (cache_is_vivt())