s390/switch_to: use generic header file

Move the switch_to() implementation to process.c and use the generic
switch_to.h header file instead, like some other architectures.

This addresses also the oddity that the old switch_to() implementation
assigns the return value of __switch_to() to 'prev' instead of 'last',
like it should.

Remove also all includes of switch_to.h from C files, except process.c.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

7 files changed, 30 insertions, 10 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 49a11f6dd7ae..f22cb6831f93 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -171,13 +171,13 @@ _LPP_OFFSET	= __LC_LPP
 	nop	0
 
 /*
- * Scheduler resume function, called by switch_to
- *  gpr2 = (task_struct *) prev
- *  gpr3 = (task_struct *) next
+ * Scheduler resume function, called by __switch_to
+ *  gpr2 = (task_struct *)prev
+ *  gpr3 = (task_struct *)next
  * Returns:
  *  gpr2 = prev
  */
-SYM_FUNC_START(__switch_to)
+SYM_FUNC_START(__switch_to_asm)
 	stmg	%r6,%r15,__SF_GPRS(%r15)	# store gprs of prev task
 	lghi	%r4,__TASK_stack
 	lghi	%r1,__TASK_thread
@@ -193,7 +193,7 @@ SYM_FUNC_START(__switch_to)
 	lmg	%r6,%r15,__SF_GPRS(%r15)	# load gprs of next task
 	ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
 	BR_EX	%r14
-SYM_FUNC_END(__switch_to)
+SYM_FUNC_END(__switch_to_asm)
 
 #if IS_ENABLED(CONFIG_KVM)
 /*
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index 9f41853f36b9..21969520f947 100644
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -19,6 +19,7 @@ void mcck_int_handler(void);
 void restart_int_handler(void);
 void early_pgm_check_handler(void);
 
+struct task_struct *__switch_to_asm(struct task_struct *prev, struct task_struct *next);
 void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs);
 void __do_pgm_check(struct pt_regs *regs);
 void __do_syscall(struct pt_regs *regs, int per_trap);
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index aa22ffc16bcd..032a1124f04b 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -13,6 +13,7 @@
 #include <linux/reboot.h>
 #include <linux/ftrace.h>
 #include <linux/debug_locks.h>
+#include <asm/guarded_storage.h>
 #include <asm/pfault.h>
 #include <asm/cio.h>
 #include <asm/setup.h>
@@ -26,7 +27,6 @@
 #include <asm/os_info.h>
 #include <asm/set_memory.h>
 #include <asm/stacktrace.h>
-#include <asm/switch_to.h>
 #include <asm/nmi.h>
 #include <asm/sclp.h>
 
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 9ad44c26d1a2..bbef8d954d01 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -28,7 +28,6 @@
 #include <asm/cputime.h>
 #include <asm/nmi.h>
 #include <asm/crw.h>
-#include <asm/switch_to.h>
 #include <asm/asm-offsets.h>
 #include <asm/pai.h>
 #include <asm/vx-insn.h>
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 4e3b366589fb..7227a73226f1 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -31,15 +31,18 @@
 #include <linux/init_task.h>
 #include <linux/entry-common.h>
 #include <linux/io.h>
+#include <asm/guarded_storage.h>
+#include <asm/access-regs.h>
+#include <asm/switch_to.h>
 #include <asm/cpu_mf.h>
 #include <asm/processor.h>
+#include <asm/ptrace.h>
 #include <asm/vtimer.h>
 #include <asm/exec.h>
 #include <asm/irq.h>
 #include <asm/nmi.h>
 #include <asm/smp.h>
 #include <asm/stacktrace.h>
-#include <asm/switch_to.h>
 #include <asm/runtime_instr.h>
 #include <asm/unwind.h>
 #include "entry.h"
@@ -190,6 +193,24 @@ void execve_tail(void)
 	asm volatile("sfpc %0" : : "d" (0));
 }
 
+struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
+{
+	/*
+	 * save_fpu_regs() sets the CIF_FPU flag, which enforces
+	 * a restore of the floating point / vector registers as
+	 * soon as the next task returns to user space.
+	 */
+	save_fpu_regs();
+	save_access_regs(&prev->thread.acrs[0]);
+	save_ri_cb(prev->thread.ri_cb);
+	save_gs_cb(prev->thread.gs_cb);
+	update_cr_regs(next);
+	restore_access_regs(&next->thread.acrs[0]);
+	restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);
+	restore_gs_cb(next->thread.gs_cb);
+	return __switch_to_asm(prev, next);
+}
+
 unsigned long __get_wchan(struct task_struct *p)
 {
 	struct unwind_state state;
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index d662ea9e54f5..7c5e99be2155 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -24,11 +24,11 @@
 #include <linux/seccomp.h>
 #include <linux/compat.h>
 #include <trace/syscall.h>
+#include <asm/guarded_storage.h>
 #include <asm/access-regs.h>
 #include <asm/page.h>
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
-#include <asm/switch_to.h>
 #include <asm/runtime_instr.h>
 #include <asm/facility.h>
 #include <asm/fpu/api.h>
diff --git a/arch/s390/kernel/uprobes.c b/arch/s390/kernel/uprobes.c
index b88345ef8bd9..5b0633ea8d93 100644
--- a/arch/s390/kernel/uprobes.c
+++ b/arch/s390/kernel/uprobes.c
@@ -12,7 +12,6 @@
 #include <linux/kdebug.h>
 #include <linux/sched/task_stack.h>
 
-#include <asm/switch_to.h>
 #include <asm/facility.h>
 #include <asm/kprobes.h>
 #include <asm/dis.h>