s390/nmi: improve revalidation of fpu / vector registers
The machine check handler will do one of two things if the floating-point
control, a floating point register or a vector register can not be
revalidated:
1) if the PSW indicates user mode the process is terminated
2) if the PSW indicates kernel mode the system is stopped
To unconditionally stop the system for 2) is incorrect.
There are three possible outcomes if the floating-point control, a
floating point register or a vector registers can not be revalidated:
1) The kernel is inside a kernel_fpu_begin/kernel_fpu_end block and
needs the register. The system is stopped.
2) No active kernel_fpu_begin/kernel_fpu_end block and the CIF_CPU bit
is not set. The user space process needs the register and is killed.
3) No active kernel_fpu_begin/kernel_fpu_end block and the CIF_FPU bit
is set. Neither the kernel nor the user space process needs the
lost register. Just revalidate it and continue.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
1 file changed