s390/fpu: Re-add exception handling in load_fpu_state()

JIRA: https://issues.redhat.com/browse/RHEL-39346
Tested: by me

commit 4734406
Author: Heiko Carstens <hca@linux.ibm.com>
Date:   Thu Jul 25 11:31:52 2024 +0200

    s390/fpu: Re-add exception handling in load_fpu_state()

    With the recent rewrite of the fpu code exception handling for the
    lfpc instruction within load_fpu_state() was erroneously removed.

    Add it again to prevent that loading invalid floating point register
    values cause an unhandled specification exception.

    Fixes: 8c09871 ("s390/fpu: limit save and restore to used registers")
    Cc: stable@vger.kernel.org
    Reported-by: Aristeu Rozanski <aris@redhat.com>
    Tested-by: Aristeu Rozanski <aris@redhat.com>
    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>

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>

Author: aristeu

arch/s390/kernel/fpu.c

@@ -113,7 +113,7 @@ void load_fpu_state(struct fpu *state, int flags)
 	int mask;
 
 	if (flags & KERNEL_FPC)
-		fpu_lfpc(&state->fpc);
+		fpu_lfpc_safe(&state->fpc);
 	if (!cpu_has_vx()) {
 		if (flags & KERNEL_VXR_V0V7)
 			load_fp_regs_vx(state->vxrs);