Merge commit 'upstream-x86-entry' into WIP.x86/mm

Pull in a minimal set of v4.15 entry code changes, for a base for the MM isolation patches.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

16 files changed, 239 insertions, 80 deletions

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5f70044340ff..d12da41f72da 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -27,7 +27,6 @@ KASAN_SANITIZE_dumpstack.o				:= n
 KASAN_SANITIZE_dumpstack_$(BITS).o			:= n
 KASAN_SANITIZE_stacktrace.o := n
 
-OBJECT_FILES_NON_STANDARD_head_$(BITS).o		:= y
 OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o	:= y
 OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o		:= y
 OBJECT_FILES_NON_STANDARD_test_nx.o			:= y
@@ -128,9 +127,9 @@ obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
 obj-$(CONFIG_TRACING)			+= tracepoint.o
 obj-$(CONFIG_SCHED_MC_PRIO)		+= itmt.o
 
-obj-$(CONFIG_ORC_UNWINDER)		+= unwind_orc.o
-obj-$(CONFIG_FRAME_POINTER_UNWINDER)	+= unwind_frame.o
-obj-$(CONFIG_GUESS_UNWINDER)		+= unwind_guess.o
+obj-$(CONFIG_UNWINDER_ORC)		+= unwind_orc.o
+obj-$(CONFIG_UNWINDER_FRAME_POINTER)	+= unwind_frame.o
+obj-$(CONFIG_UNWINDER_GUESS)		+= unwind_guess.o
 
 ###
 # 64 bit specific files
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index c60922a66385..90cb82dbba57 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -23,6 +23,7 @@ obj-y			+= rdrand.o
 obj-y			+= match.o
 obj-y			+= bugs.o
 obj-$(CONFIG_CPU_FREQ)	+= aperfmperf.o
+obj-y			+= cpuid-deps.o
 
 obj-$(CONFIG_PROC_FS)	+= proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c9176bae7fd8..cdf79ab628c2 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1301,18 +1301,16 @@ void print_cpu_info(struct cpuinfo_x86 *c)
 		pr_cont(")\n");
 }
 
-static __init int setup_disablecpuid(char *arg)
+/*
+ * clearcpuid= was already parsed in fpu__init_parse_early_param.
+ * But we need to keep a dummy __setup around otherwise it would
+ * show up as an environment variable for init.
+ */
+static __init int setup_clearcpuid(char *arg)
 {
-	int bit;
-
-	if (get_option(&arg, &bit) && bit >= 0 && bit < NCAPINTS * 32)
-		setup_clear_cpu_cap(bit);
-	else
-		return 0;
-
 	return 1;
 }
-__setup("clearcpuid=", setup_disablecpuid);
+__setup("clearcpuid=", setup_clearcpuid);
 
 #ifdef CONFIG_X86_64
 DEFINE_PER_CPU_FIRST(union irq_stack_union,
@@ -1572,9 +1570,13 @@ void cpu_init(void)
 	initialize_tlbstate_and_flush();
 	enter_lazy_tlb(&init_mm, me);
 
-	load_sp0(t, &current->thread);
+	/*
+	 * Initialize the TSS.  Don't bother initializing sp0, as the initial
+	 * task never enters user mode.
+	 */
 	set_tss_desc(cpu, t);
 	load_TR_desc();
+
 	load_mm_ldt(&init_mm);
 
 	clear_all_debug_regs();
@@ -1596,7 +1598,6 @@ void cpu_init(void)
 	int cpu = smp_processor_id();
 	struct task_struct *curr = current;
 	struct tss_struct *t = &per_cpu(cpu_tss, cpu);
-	struct thread_struct *thread = &curr->thread;
 
 	wait_for_master_cpu(cpu);
 
@@ -1627,9 +1628,13 @@ void cpu_init(void)
 	initialize_tlbstate_and_flush();
 	enter_lazy_tlb(&init_mm, curr);
 
-	load_sp0(t, thread);
+	/*
+	 * Initialize the TSS.  Don't bother initializing sp0, as the initial
+	 * task never enters user mode.
+	 */
 	set_tss_desc(cpu, t);
 	load_TR_desc();
+
 	load_mm_ldt(&init_mm);
 
 	t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
new file mode 100644
index 000000000000..c21f22d836ad
--- /dev/null
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -0,0 +1,125 @@
+/* Declare dependencies between CPUIDs */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <asm/cpufeature.h>
+
+struct cpuid_dep {
+	unsigned int	feature;
+	unsigned int	depends;
+};
+
+/*
+ * Table of CPUID features that depend on others.
+ *
+ * This only includes dependencies that can be usefully disabled, not
+ * features part of the base set (like FPU).
+ *
+ * Note this all is not __init / __initdata because it can be
+ * called from cpu hotplug. It shouldn't do anything in this case,
+ * but it's difficult to tell that to the init reference checker.
+ */
+const static struct cpuid_dep cpuid_deps[] = {
+	{ X86_FEATURE_XSAVEOPT,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_XSAVEC,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_XSAVES,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_AVX,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_PKU,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_MPX,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_XGETBV1,		X86_FEATURE_XSAVE     },
+	{ X86_FEATURE_FXSR_OPT,		X86_FEATURE_FXSR      },
+	{ X86_FEATURE_XMM,		X86_FEATURE_FXSR      },
+	{ X86_FEATURE_XMM2,		X86_FEATURE_XMM       },
+	{ X86_FEATURE_XMM3,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_XMM4_1,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_XMM4_2,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_XMM3,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_PCLMULQDQ,	X86_FEATURE_XMM2      },
+	{ X86_FEATURE_SSSE3,		X86_FEATURE_XMM2,     },
+	{ X86_FEATURE_F16C,		X86_FEATURE_XMM2,     },
+	{ X86_FEATURE_AES,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_SHA_NI,		X86_FEATURE_XMM2      },
+	{ X86_FEATURE_FMA,		X86_FEATURE_AVX       },
+	{ X86_FEATURE_AVX2,		X86_FEATURE_AVX,      },
+	{ X86_FEATURE_AVX512F,		X86_FEATURE_AVX,      },
+	{ X86_FEATURE_AVX512IFMA,	X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512PF,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512ER,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512CD,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512DQ,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512BW,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512VL,		X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512VBMI,	X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512_VBMI2,	X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_GFNI,		X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_VAES,		X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_VPCLMULQDQ,	X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_AVX512_VNNI,	X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_AVX512_BITALG,	X86_FEATURE_AVX512VL  },
+	{ X86_FEATURE_AVX512_4VNNIW,	X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512_4FMAPS,	X86_FEATURE_AVX512F   },
+	{ X86_FEATURE_AVX512_VPOPCNTDQ, X86_FEATURE_AVX512F   },
+	{}
+};
+
+static inline void __clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit)
+{
+	clear_bit32(bit, c->x86_capability);
+}
+
+static inline void __setup_clear_cpu_cap(unsigned int bit)
+{
+	clear_cpu_cap(&boot_cpu_data, bit);
+	set_bit32(bit, cpu_caps_cleared);
+}
+
+static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
+{
+	if (!c)
+		__setup_clear_cpu_cap(feature);
+	else
+		__clear_cpu_cap(c, feature);
+}
+
+/* Take the capabilities and the BUG bits into account */
+#define MAX_FEATURE_BITS ((NCAPINTS + NBUGINTS) * sizeof(u32) * 8)
+
+static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
+{
+	DECLARE_BITMAP(disable, MAX_FEATURE_BITS);
+	const struct cpuid_dep *d;
+	bool changed;
+
+	if (WARN_ON(feature >= MAX_FEATURE_BITS))
+		return;
+
+	clear_feature(c, feature);
+
+	/* Collect all features to disable, handling dependencies */
+	memset(disable, 0, sizeof(disable));
+	__set_bit(feature, disable);
+
+	/* Loop until we get a stable state. */
+	do {
+		changed = false;
+		for (d = cpuid_deps; d->feature; d++) {
+			if (!test_bit(d->depends, disable))
+				continue;
+			if (__test_and_set_bit(d->feature, disable))
+				continue;
+
+			changed = true;
+			clear_feature(c, d->feature);
+		}
+	} while (changed);
+}
+
+void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
+{
+	do_clear_cpu_cap(c, feature);
+}
+
+void setup_clear_cpu_cap(unsigned int feature)
+{
+	do_clear_cpu_cap(NULL, feature);
+}
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 7affb7e3d9a5..6abd83572b01 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -249,6 +249,10 @@ static void __init fpu__init_system_ctx_switch(void)
  */
 static void __init fpu__init_parse_early_param(void)
 {
+	char arg[32];
+	char *argptr = arg;
+	int bit;
+
 	if (cmdline_find_option_bool(boot_command_line, "no387"))
 		setup_clear_cpu_cap(X86_FEATURE_FPU);
 
@@ -266,6 +270,13 @@ static void __init fpu__init_parse_early_param(void)
 
 	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
 		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+
+	if (cmdline_find_option(boot_command_line, "clearcpuid", arg,
+				sizeof(arg)) &&
+	    get_option(&argptr, &bit) &&
+	    bit >= 0 &&
+	    bit < NCAPINTS * 32)
+		setup_clear_cpu_cap(bit);
 }
 
 /*
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index f1d5476c9022..87a57b7642d3 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -15,6 +15,7 @@
 #include <asm/fpu/xstate.h>
 
 #include <asm/tlbflush.h>
+#include <asm/cpufeature.h>
 
 /*
  * Although we spell it out in here, the Processor Trace
@@ -36,6 +37,19 @@ static const char *xfeature_names[] =
 	"unknown xstate feature"	,
 };
 
+static short xsave_cpuid_features[] __initdata = {
+	X86_FEATURE_FPU,
+	X86_FEATURE_XMM,
+	X86_FEATURE_AVX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_INTEL_PT,
+	X86_FEATURE_PKU,
+};
+
 /*
  * Mask of xstate features supported by the CPU and the kernel:
  */
@@ -59,26 +73,6 @@ unsigned int fpu_user_xstate_size;
 void fpu__xstate_clear_all_cpu_caps(void)
 {
 	setup_clear_cpu_cap(X86_FEATURE_XSAVE);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVES);
-	setup_clear_cpu_cap(X86_FEATURE_AVX);
-	setup_clear_cpu_cap(X86_FEATURE_AVX2);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512F);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512IFMA);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512DQ);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512BW);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512VL);
-	setup_clear_cpu_cap(X86_FEATURE_MPX);
-	setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512VBMI);
-	setup_clear_cpu_cap(X86_FEATURE_PKU);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_4VNNIW);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_4FMAPS);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_VPOPCNTDQ);
 }
 
 /*
@@ -726,6 +720,7 @@ void __init fpu__init_system_xstate(void)
 	unsigned int eax, ebx, ecx, edx;
 	static int on_boot_cpu __initdata = 1;
 	int err;
+	int i;
 
 	WARN_ON_FPU(!on_boot_cpu);
 	on_boot_cpu = 0;
@@ -759,6 +754,14 @@ void __init fpu__init_system_xstate(void)
 		goto out_disable;
 	}
 
+	/*
+	 * Clear XSAVE features that are disabled in the normal CPUID.
+	 */
+	for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
+		if (!boot_cpu_has(xsave_cpuid_features[i]))
+			xfeatures_mask &= ~BIT(i);
+	}
+
 	xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
 	/* Enable xstate instructions to be able to continue with initialization: */
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index f1d528bb66a6..c29020907886 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -212,9 +212,6 @@ ENTRY(startup_32_smp)
 #endif
 
 .Ldefault_entry:
-#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
-			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
-			 X86_CR0_PG)
 	movl $(CR0_STATE & ~X86_CR0_PG),%eax
 	movl %eax,%cr0
 
@@ -402,7 +399,7 @@ ENTRY(early_idt_handler_array)
 	# 24(%rsp) error code
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
-	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
+	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
 	pushl $0		# Dummy error code, to make stack frame uniform
 	.endif
 	pushl $i		# 20(%esp) Vector number
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 6dde3f3fc1f8..fd58835d8f9b 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -50,6 +50,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
 	.code64
 	.globl startup_64
 startup_64:
+	UNWIND_HINT_EMPTY
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 	 * and someone has loaded an identity mapped page table
@@ -89,6 +90,7 @@ startup_64:
 	addq	$(early_top_pgt - __START_KERNEL_map), %rax
 	jmp 1f
 ENTRY(secondary_startup_64)
+	UNWIND_HINT_EMPTY
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 	 * and someone has loaded a mapped page table.
@@ -133,6 +135,7 @@ ENTRY(secondary_startup_64)
 	movq	$1f, %rax
 	jmp	*%rax
 1:
+	UNWIND_HINT_EMPTY
 
 	/* Check if nx is implemented */
 	movl	$0x80000001, %eax
@@ -150,9 +153,6 @@ ENTRY(secondary_startup_64)
 1:	wrmsr				/* Make changes effective */
 
 	/* Setup cr0 */
-#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
-			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
-			 X86_CR0_PG)
 	movl	$CR0_STATE, %eax
 	/* Make changes effective */
 	movq	%rax, %cr0
@@ -235,7 +235,7 @@ ENTRY(secondary_startup_64)
 	pushq	%rax		# target address in negative space
 	lretq
 .Lafter_lret:
-ENDPROC(secondary_startup_64)
+END(secondary_startup_64)
 
 #include "verify_cpu.S"
 
@@ -247,6 +247,7 @@ ENDPROC(secondary_startup_64)
  */
 ENTRY(start_cpu0)
 	movq	initial_stack(%rip), %rsp
+	UNWIND_HINT_EMPTY
 	jmp	.Ljump_to_C_code
 ENDPROC(start_cpu0)
 #endif
@@ -266,26 +267,24 @@ ENDPROC(start_cpu0)
 	.quad  init_thread_union + THREAD_SIZE - SIZEOF_PTREGS
 	__FINITDATA
 
-bad_address:
-	jmp bad_address
-
 	__INIT
 ENTRY(early_idt_handler_array)
-	# 104(%rsp) %rflags
-	#  96(%rsp) %cs
-	#  88(%rsp) %rip
-	#  80(%rsp) error code
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
-	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
-	pushq $0		# Dummy error code, to make stack frame uniform
+	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
+		UNWIND_HINT_IRET_REGS
+		pushq $0	# Dummy error code, to make stack frame uniform
+	.else
+		UNWIND_HINT_IRET_REGS offset=8
 	.endif
 	pushq $i		# 72(%rsp) Vector number
 	jmp early_idt_handler_common
+	UNWIND_HINT_IRET_REGS
 	i = i + 1
 	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
 	.endr
-ENDPROC(early_idt_handler_array)
+	UNWIND_HINT_IRET_REGS offset=16
+END(early_idt_handler_array)
 
 early_idt_handler_common:
 	/*
@@ -313,6 +312,7 @@ early_idt_handler_common:
 	pushq %r13				/* pt_regs->r13 */
 	pushq %r14				/* pt_regs->r14 */
 	pushq %r15				/* pt_regs->r15 */
+	UNWIND_HINT_REGS
 
 	cmpq $14,%rsi		/* Page fault? */
 	jnz 10f
@@ -327,8 +327,8 @@ early_idt_handler_common:
 
 20:
 	decl early_recursion_flag(%rip)
-	jmp restore_regs_and_iret
-ENDPROC(early_idt_handler_common)
+	jmp restore_regs_and_return_to_kernel
+END(early_idt_handler_common)
 
 	__INITDATA
 
@@ -435,7 +435,7 @@ ENTRY(phys_base)
 EXPORT_SYMBOL(phys_base)
 
 #include "../../x86/xen/xen-head.S"
-	
+
 	__PAGE_ALIGNED_BSS
 NEXT_PAGE(empty_zero_page)
 	.skip PAGE_SIZE
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 4d17bacf4030..ae5615b03def 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -13,6 +13,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
+#include <linux/syscalls.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/uaccess.h>
@@ -295,8 +296,8 @@ out:
 	return error;
 }
 
-asmlinkage int sys_modify_ldt(int func, void __user *ptr,
-			      unsigned long bytecount)
+SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr ,
+		unsigned long , bytecount)
 {
 	int ret = -ENOSYS;
 
@@ -314,5 +315,14 @@ asmlinkage int sys_modify_ldt(int func, void __user *ptr,
 		ret = write_ldt(ptr, bytecount, 0);
 		break;
 	}
-	return ret;
+	/*
+	 * The SYSCALL_DEFINE() macros give us an 'unsigned long'
+	 * return type, but tht ABI for sys_modify_ldt() expects
+	 * 'int'.  This cast gives us an int-sized value in %rax
+	 * for the return code.  The 'unsigned' is necessary so
+	 * the compiler does not try to sign-extend the negative
+	 * return codes into the high half of the register when
+	 * taking the value from int->long.
+	 */
+	return (unsigned int)ret;
 }
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c67685337c5a..97fb3e5737f5 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -49,7 +49,13 @@
  */
 __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
 	.x86_tss = {
-		.sp0 = TOP_OF_INIT_STACK,
+		/*
+		 * .sp0 is only used when entering ring 0 from a lower
+		 * privilege level.  Since the init task never runs anything
+		 * but ring 0 code, there is no need for a valid value here.
+		 * Poison it.
+		 */
+		.sp0 = (1UL << (BITS_PER_LONG-1)) + 1,
 #ifdef CONFIG_X86_32
 		.ss0 = __KERNEL_DS,
 		.ss1 = __KERNEL_CS,
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 11966251cd42..45bf0c5f93e1 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -284,9 +284,11 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	/*
 	 * Reload esp0 and cpu_current_top_of_stack.  This changes
-	 * current_thread_info().
+	 * current_thread_info().  Refresh the SYSENTER configuration in
+	 * case prev or next is vm86.
 	 */
-	load_sp0(tss, next);
+	update_sp0(next_p);
+	refresh_sysenter_cs(next);
 	this_cpu_write(cpu_current_top_of_stack,
 		       (unsigned long)task_stack_page(next_p) +
 		       THREAD_SIZE);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 302e7b2572d1..eeeb34f85c25 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -274,7 +274,6 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	struct inactive_task_frame *frame;
 	struct task_struct *me = current;
 
-	p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 	childregs = task_pt_regs(p);
 	fork_frame = container_of(childregs, struct fork_frame, regs);
 	frame = &fork_frame->frame;
@@ -464,8 +463,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	 */
 	this_cpu_write(current_task, next_p);
 
-	/* Reload esp0 and ss1.  This changes current_thread_info(). */
-	load_sp0(tss, next);
+	/* Reload sp0. */
+	update_sp0(next_p);
 
 	/*
 	 * Now maybe reload the debug registers and handle I/O bitmaps
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 65a0ccdc3050..d56c1d209283 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -962,8 +962,7 @@ void common_cpu_up(unsigned int cpu, struct task_struct *idle)
 #ifdef CONFIG_X86_32
 	/* Stack for startup_32 can be just as for start_secondary onwards */
 	irq_ctx_init(cpu);
-	per_cpu(cpu_current_top_of_stack, cpu) =
-		(unsigned long)task_stack_page(idle) + THREAD_SIZE;
+	per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
 #else
 	initial_gs = per_cpu_offset(cpu);
 #endif
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 5a6b8f809792..d366adfc61da 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -141,8 +141,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
 	 * will catch asm bugs and any attempt to use ist_preempt_enable
 	 * from double_fault.
 	 */
-	BUG_ON((unsigned long)(current_top_of_stack() -
-			       current_stack_pointer) >= THREAD_SIZE);
+	BUG_ON(!on_thread_stack());
 
 	preempt_enable_no_resched();
 }
diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
index 014ea59aa153..3d3c2f71f617 100644
--- a/arch/x86/kernel/verify_cpu.S
+++ b/arch/x86/kernel/verify_cpu.S
@@ -33,7 +33,7 @@
 #include <asm/cpufeatures.h>
 #include <asm/msr-index.h>
 
-verify_cpu:
+ENTRY(verify_cpu)
 	pushf				# Save caller passed flags
 	push	$0			# Kill any dangerous flags
 	popf
@@ -139,3 +139,4 @@ verify_cpu:
 	popf				# Restore caller passed flags
 	xorl %eax, %eax
 	ret
+ENDPROC(verify_cpu)
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 68244742ecb0..5edb27f1a2c4 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -55,6 +55,7 @@
 #include <asm/irq.h>
 #include <asm/traps.h>
 #include <asm/vm86.h>
+#include <asm/switch_to.h>
 
 /*
  * Known problems:
@@ -94,7 +95,6 @@
 
 void save_v86_state(struct kernel_vm86_regs *regs, int retval)
 {
-	struct tss_struct *tss;
 	struct task_struct *tsk = current;
 	struct vm86plus_struct __user *user;
 	struct vm86 *vm86 = current->thread.vm86;
@@ -146,12 +146,13 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval)
 		do_exit(SIGSEGV);
 	}
 
-	tss = &per_cpu(cpu_tss, get_cpu());
+	preempt_disable();
 	tsk->thread.sp0 = vm86->saved_sp0;
 	tsk->thread.sysenter_cs = __KERNEL_CS;
-	load_sp0(tss, &tsk->thread);
+	update_sp0(tsk);
+	refresh_sysenter_cs(&tsk->thread);
 	vm86->saved_sp0 = 0;
-	put_cpu();
+	preempt_enable();
 
 	memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
 
@@ -237,7 +238,6 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
 
 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
 {
-	struct tss_struct *tss;
 	struct task_struct *tsk = current;
 	struct vm86 *vm86 = tsk->thread.vm86;
 	struct kernel_vm86_regs vm86regs;
@@ -365,15 +365,17 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
 	vm86->saved_sp0 = tsk->thread.sp0;
 	lazy_save_gs(vm86->regs32.gs);
 
-	tss = &per_cpu(cpu_tss, get_cpu());
 	/* make room for real-mode segments */
+	preempt_disable();
 	tsk->thread.sp0 += 16;
 
-	if (static_cpu_has(X86_FEATURE_SEP))
+	if (static_cpu_has(X86_FEATURE_SEP)) {
 		tsk->thread.sysenter_cs = 0;
+		refresh_sysenter_cs(&tsk->thread);
+	}
 
-	load_sp0(tss, &tsk->thread);
-	put_cpu();
+	update_sp0(tsk);
+	preempt_enable();
 
 	if (vm86->flags & VM86_SCREEN_BITMAP)
 		mark_screen_rdonly(tsk->mm);