2 files changed, 29 insertions, 16 deletions

diff --git a/arch/s390/include/asm/fpu/api.h b/arch/s390/include/asm/fpu/api.h
index 9acf48e53a..d6ca8bc6ca 100644
--- a/arch/s390/include/asm/fpu/api.h
+++ b/arch/s390/include/asm/fpu/api.h
@@ -46,26 +46,33 @@
 
 #include <linux/preempt.h>
 #include <asm/asm-extable.h>
+#include <asm/fpu/internal.h>
 
 void save_fpu_regs(void);
 void load_fpu_regs(void);
 void __load_fpu_regs(void);
 
-static inline int test_fp_ctl(u32 fpc)
+/**
+ * sfpc_safe - Set floating point control register safely.
+ * @fpc: new value for floating point control register
+ *
+ * Set floating point control register. This may lead to an exception,
+ * since a saved value may have been modified by user space (ptrace,
+ * signal return, kvm registers) to an invalid value. In such a case
+ * set the floating point control register to zero.
+ */
+static inline void sfpc_safe(u32 fpc)
 {
-	u32 orig_fpc;
-	int rc;
-
-	asm volatile(
-		"	efpc    %1\n"
-		"	sfpc	%2\n"
-		"0:	sfpc	%1\n"
-		"	la	%0,0\n"
-		"1:\n"
-		EX_TABLE(0b,1b)
-		: "=d" (rc), "=&d" (orig_fpc)
-		: "d" (fpc), "0" (-EINVAL));
-	return rc;
+	asm volatile("\n"
+		"0:	sfpc	%[fpc]\n"
+		"1:	nopr	%%r7\n"
+		".pushsection .fixup, \"ax\"\n"
+		"2:	lghi	%[fpc],0\n"
+		"	jg	0b\n"
+		".popsection\n"
+		EX_TABLE(1b, 2b)
+		: [fpc] "+d" (fpc)
+		: : "memory");
 }
 
 #define KERNEL_FPC		1
diff --git a/arch/s390/include/asm/fpu/internal.h b/arch/s390/include/asm/fpu/internal.h
index 8634581b90..d511c4cf5a 100644
--- a/arch/s390/include/asm/fpu/internal.h
+++ b/arch/s390/include/asm/fpu/internal.h
@@ -10,8 +10,14 @@
 #define _ASM_S390_FPU_INTERNAL_H
 
 #include <linux/string.h>
+#include <asm/facility.h>
 #include <asm/fpu/types.h>
 
+static inline bool cpu_has_vx(void)
+{
+	return likely(test_facility(129));
+}
+
 static inline void save_vx_regs(__vector128 *vxrs)
 {
 	asm volatile(
@@ -41,7 +47,7 @@ static inline void fpregs_store(_s390_fp_regs *fpregs, struct fpu *fpu)
 {
 	fpregs->pad = 0;
 	fpregs->fpc = fpu->fpc;
-	if (MACHINE_HAS_VX)
+	if (cpu_has_vx())
 		convert_vx_to_fp((freg_t *)&fpregs->fprs, fpu->vxrs);
 	else
 		memcpy((freg_t *)&fpregs->fprs, fpu->fprs,
@@ -51,7 +57,7 @@ static inline void fpregs_store(_s390_fp_regs *fpregs, struct fpu *fpu)
 static inline void fpregs_load(_s390_fp_regs *fpregs, struct fpu *fpu)
 {
 	fpu->fpc = fpregs->fpc;
-	if (MACHINE_HAS_VX)
+	if (cpu_has_vx())
 		convert_fp_to_vx(fpu->vxrs, (freg_t *)&fpregs->fprs);
 	else
 		memcpy(fpu->fprs, (freg_t *)&fpregs->fprs,