s390/fpu: always enable the vector facility if it is available

If the kernel detects that the s390 hardware supports the vector
facility, it is enabled by default at an early stage.  To force
it off, use the novx kernel parameter.  Note that there is a small
time window, where the vector facility is enabled before it is
forced to be off.

With enabling the vector facility by default, the FPU save and
restore functions can be improved.  They do not longer require
to manage expensive control register updates to enable or disable
the vector enablement control for particular processes.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 15 insertions, 29 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 8b1c8e3..3ccd900 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -239,7 +239,7 @@ static unsigned long __peek_user(struct task_struct *child, addr_t addr)
 		 * or the child->thread.fpu.vxrs array
 		 */
 		offset = addr - (addr_t) &dummy->regs.fp_regs.fprs;
-		if (is_vx_task(child))
+		if (MACHINE_HAS_VX)
 			tmp = *(addr_t *)
 			       ((addr_t) child->thread.fpu.vxrs + 2*offset);
 		else
@@ -383,7 +383,7 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
 		 * or the child->thread.fpu.vxrs array
 		 */
 		offset = addr - (addr_t) &dummy->regs.fp_regs.fprs;
-		if (is_vx_task(child))
+		if (MACHINE_HAS_VX)
 			*(addr_t *)((addr_t)
 				child->thread.fpu.vxrs + 2*offset) = data;
 		else
@@ -617,7 +617,7 @@ static u32 __peek_user_compat(struct task_struct *child, addr_t addr)
 		 * or the child->thread.fpu.vxrs array
 		 */
 		offset = addr - (addr_t) &dummy32->regs.fp_regs.fprs;
-		if (is_vx_task(child))
+		if (MACHINE_HAS_VX)
 			tmp = *(__u32 *)
 			       ((addr_t) child->thread.fpu.vxrs + 2*offset);
 		else
@@ -742,7 +742,7 @@ static int __poke_user_compat(struct task_struct *child,
 		 * or the child->thread.fpu.vxrs array
 		 */
 		offset = addr - (addr_t) &dummy32->regs.fp_regs.fprs;
-		if (is_vx_task(child))
+		if (MACHINE_HAS_VX)
 			*(__u32 *)((addr_t)
 				child->thread.fpu.vxrs + 2*offset) = tmp;
 		else
@@ -981,7 +981,7 @@ static int s390_fpregs_set(struct task_struct *target,
 	if (rc)
 		return rc;
 
-	if (is_vx_task(target))
+	if (MACHINE_HAS_VX)
 		convert_fp_to_vx(target->thread.fpu.vxrs, fprs);
 	else
 		memcpy(target->thread.fpu.fprs, &fprs, sizeof(fprs));
@@ -1047,13 +1047,10 @@ static int s390_vxrs_low_get(struct task_struct *target,
 
 	if (!MACHINE_HAS_VX)
 		return -ENODEV;
-	if (is_vx_task(target)) {
-		if (target == current)
-			save_fpu_regs();
-		for (i = 0; i < __NUM_VXRS_LOW; i++)
-			vxrs[i] = *((__u64 *)(target->thread.fpu.vxrs + i) + 1);
-	} else
-		memset(vxrs, 0, sizeof(vxrs));
+	if (target == current)
+		save_fpu_regs();
+	for (i = 0; i < __NUM_VXRS_LOW; i++)
+		vxrs[i] = *((__u64 *)(target->thread.fpu.vxrs + i) + 1);
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
 }
 
@@ -1067,11 +1064,7 @@ static int s390_vxrs_low_set(struct task_struct *target,
 
 	if (!MACHINE_HAS_VX)
 		return -ENODEV;
-	if (!is_vx_task(target)) {
-		rc = alloc_vector_registers(target);
-		if (rc)
-			return rc;
-	} else if (target == current)
+	if (target == current)
 		save_fpu_regs();
 
 	rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
@@ -1091,13 +1084,10 @@ static int s390_vxrs_high_get(struct task_struct *target,
 
 	if (!MACHINE_HAS_VX)
 		return -ENODEV;
-	if (is_vx_task(target)) {
-		if (target == current)
-			save_fpu_regs();
-		memcpy(vxrs, target->thread.fpu.vxrs + __NUM_VXRS_LOW,
-		       sizeof(vxrs));
-	} else
-		memset(vxrs, 0, sizeof(vxrs));
+	if (target == current)
+		save_fpu_regs();
+	memcpy(vxrs, target->thread.fpu.vxrs + __NUM_VXRS_LOW, sizeof(vxrs));
+
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
 }
 
@@ -1110,11 +1100,7 @@ static int s390_vxrs_high_set(struct task_struct *target,
 
 	if (!MACHINE_HAS_VX)
 		return -ENODEV;
-	if (!is_vx_task(target)) {
-		rc = alloc_vector_registers(target);
-		if (rc)
-			return rc;
-	} else if (target == current)
+	if (target == current)
 		save_fpu_regs();
 
 	rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf,