6 files changed, 8 insertions, 33 deletions

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 8b3ed21c9191..185142b84ebe 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -314,11 +314,6 @@ struct x86_hw_tss {
 struct x86_hw_tss {
 	u32			reserved1;
 	u64			sp0;
-
-	/*
-	 * We store cpu_current_top_of_stack in sp1 so it's always accessible.
-	 * Linux does not use ring 1, so sp1 is not otherwise needed.
-	 */
 	u64			sp1;
 
 	/*
@@ -426,12 +421,7 @@ struct irq_stack {
 	char		stack[IRQ_STACK_SIZE];
 } __aligned(IRQ_STACK_SIZE);
 
-#ifdef CONFIG_X86_32
 DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack);
-#else
-/* The RO copy can't be accessed with this_cpu_xyz(), so use the RW copy. */
-#define cpu_current_top_of_stack cpu_tss_rw.x86_tss.sp1
-#endif
 
 #ifdef CONFIG_X86_64
 struct fixed_percpu_data {
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 9f69cc497f4b..b5f0d2ff47e4 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -71,12 +71,7 @@ static inline void update_task_stack(struct task_struct *task)
 	else
 		this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
 #else
-	/*
-	 * x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That
-	 * doesn't work on x86-32 because sp1 and
-	 * cpu_current_top_of_stack have different values (because of
-	 * the non-zero stack-padding on 32bit).
-	 */
+	/* Xen PV enters the kernel on the thread stack. */
 	if (static_cpu_has(X86_FEATURE_XENPV))
 		load_sp0(task_top_of_stack(task));
 #endif
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 06b740bae431..de406d93b515 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -197,13 +197,7 @@ static inline int arch_within_stack_frames(const void * const stack,
 #endif
 }
 
-#else /* !__ASSEMBLY__ */
-
-#ifdef CONFIG_X86_64
-# define cpu_current_top_of_stack (cpu_tss_rw + TSS_sp1)
-#endif
-
-#endif
+#endif  /* !__ASSEMBLY__ */
 
 /*
  * Thread-synchronous status.
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1aa5f0ac598f..340107800b36 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1748,6 +1748,8 @@ DEFINE_PER_CPU(bool, hardirq_stack_inuse);
 DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
 EXPORT_PER_CPU_SYMBOL(__preempt_count);
 
+DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) = TOP_OF_INIT_STACK;
+
 /* May not be marked __init: used by software suspend */
 void syscall_init(void)
 {
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index cdfe5b4e99b3..43cbfc84153a 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -63,14 +63,9 @@ __visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = {
 		 */
 		.sp0 = (1UL << (BITS_PER_LONG-1)) + 1,
 
-		/*
-		 * .sp1 is cpu_current_top_of_stack.  The init task never
-		 * runs user code, but cpu_current_top_of_stack should still
-		 * be well defined before the first context switch.
-		 */
+#ifdef CONFIG_X86_32
 		.sp1 = TOP_OF_INIT_STACK,
 
-#ifdef CONFIG_X86_32
 		.ss0 = __KERNEL_DS,
 		.ss1 = __KERNEL_CS,
 #endif
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index b377604fb112..5d5c7bb50ce9 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -440,10 +440,9 @@ static void __init pti_clone_user_shared(void)
 
 	for_each_possible_cpu(cpu) {
 		/*
-		 * The SYSCALL64 entry code needs to be able to find the
-		 * thread stack and needs one word of scratch space in which
-		 * to spill a register.  All of this lives in the TSS, in
-		 * the sp1 and sp2 slots.
+		 * The SYSCALL64 entry code needs one word of scratch space
+		 * in which to spill a register.  It lives in the sp2 slot
+		 * of the CPU's TSS.
 		 *
 		 * This is done for all possible CPUs during boot to ensure
 		 * that it's propagated to all mms.