s390/diag: Convert MACHINE_HAS_DIAG9C to machine_has_diag9c()

Use static branch(es) to implement and use machine_has_diag9c() instead of
a runtime check via MACHINE_HAS_DIAG9C.

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/startup.c

@@ -49,6 +49,37 @@ void error(char *x)
 	disabled_wait();
 }
 
+static void detect_diag9c(void)
+{
+	unsigned long reg1, reg2;
+	unsigned int cpu;
+	int rc = 1;
+	psw_t old;
+
+	cpu = stap();
+	asm volatile(
+		"	mvc	0(16,%[psw_old]),0(%[psw_pgm])\n"
+		"	epsw	%[reg1],%[reg2]\n"
+		"	st	%[reg1],0(%[psw_pgm])\n"
+		"	st	%[reg2],4(%[psw_pgm])\n"
+		"	larl	%[reg1],1f\n"
+		"	stg	%[reg1],8(%[psw_pgm])\n"
+		"	diag	%[cpu],0,0x9c\n"
+		"	lhi	%[rc],0\n"
+		"1:	mvc	0(16,%[psw_pgm]),0(%[psw_old])\n"
+		: [reg1] "=&d" (reg1),
+		  [reg2] "=&a" (reg2),
+		  [rc] "+&d" (rc),
+		  "+Q" (get_lowcore()->program_new_psw),
+		  "=Q" (old)
+		: [psw_old] "a" (&old),
+		  [psw_pgm] "a" (&get_lowcore()->program_new_psw),
+		  [cpu] "d" (cpu)
+		: "cc", "memory");
+	if (!rc)
+		set_machine_feature(MFEATURE_DIAG9C);
+}
+
 static void reset_tod_clock(void)
 {
 	union tod_clock clk;
@@ -488,6 +519,7 @@ void startup_kernel(void)
 	sclp_early_read_info();
 	sclp_early_detect_machine_features();
 	detect_facilities();
+	detect_diag9c();
 	cmma_init();
 	sanitize_prot_virt_host();
 	max_physmem_end = detect_max_physmem_end();

arch/s390/include/asm/machine.h

@@ -14,6 +14,7 @@
 #define MFEATURE_TLB_GUEST	3
 #define MFEATURE_TX		4
 #define MFEATURE_ESOP		5
+#define MFEATURE_DIAG9C		6
 
 #ifndef __ASSEMBLY__
 
@@ -86,6 +87,7 @@ DEFINE_MACHINE_HAS_FEATURE(scc, MFEATURE_SCC)
 DEFINE_MACHINE_HAS_FEATURE(tlb_guest, MFEATURE_TLB_GUEST)
 DEFINE_MACHINE_HAS_FEATURE(tx, MFEATURE_TX)
 DEFINE_MACHINE_HAS_FEATURE(esop, MFEATURE_ESOP)
+DEFINE_MACHINE_HAS_FEATURE(diag9c, MFEATURE_DIAG9C)
 
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_S390_MACHINE_H */

arch/s390/include/asm/setup.h

@@ -20,7 +20,6 @@
 #define MACHINE_FLAG_VM		BIT(0)
 #define MACHINE_FLAG_KVM	BIT(1)
 #define MACHINE_FLAG_LPAR	BIT(2)
-#define MACHINE_FLAG_DIAG9C	BIT(3)
 
 #define LPP_MAGIC		BIT(31)
 #define LPP_PID_MASK		_AC(0xffffffff, UL)
@@ -68,8 +67,6 @@ extern unsigned long mio_wb_bit_mask;
 #define MACHINE_IS_KVM		(get_lowcore()->machine_flags & MACHINE_FLAG_KVM)
 #define MACHINE_IS_LPAR		(get_lowcore()->machine_flags & MACHINE_FLAG_LPAR)
 
-#define MACHINE_HAS_DIAG9C	(get_lowcore()->machine_flags & MACHINE_FLAG_DIAG9C)
-
 /*
  * Console mode. Override with conmode=
  */

arch/s390/kernel/early.c

@@ -203,23 +203,6 @@ static noinline __init void setup_lowcore_early(void)
 	lc->return_mcck_lpswe = gen_lpswe(__LC_RETURN_MCCK_PSW);
 }
 
-static __init void detect_diag9c(void)
-{
-	unsigned int cpu_address;
-	int rc;
-
-	cpu_address = stap();
-	diag_stat_inc(DIAG_STAT_X09C);
-	asm volatile(
-		"	diag	%2,0,0x9c\n"
-		"0:	la	%0,0\n"
-		"1:\n"
-		EX_TABLE(0b,1b)
-		: "=d" (rc) : "0" (-EOPNOTSUPP), "d" (cpu_address) : "cc");
-	if (!rc)
-		get_lowcore()->machine_flags |= MACHINE_FLAG_DIAG9C;
-}
-
 static __init void detect_machine_facilities(void)
 {
 	if (test_facility(129))
@@ -269,7 +252,6 @@ void __init startup_init(void)
 	detect_machine_type();
 	setup_arch_string();
 	setup_boot_command_line();
-	detect_diag9c();
 	detect_machine_facilities();
 	save_vector_registers();
 	setup_topology();

arch/s390/kernel/smp.c

@@ -39,6 +39,7 @@
 #include <linux/kprobes.h>
 #include <asm/access-regs.h>
 #include <asm/asm-offsets.h>
+#include <asm/machine.h>
 #include <asm/ctlreg.h>
 #include <asm/pfault.h>
 #include <asm/diag.h>
@@ -417,7 +418,7 @@ EXPORT_SYMBOL(arch_vcpu_is_preempted);
 
 void notrace smp_yield_cpu(int cpu)
 {
-	if (!MACHINE_HAS_DIAG9C)
+	if (!machine_has_diag9c())
 		return;
 	diag_stat_inc_norecursion(DIAG_STAT_X09C);
 	asm volatile("diag %0,0,0x9c"