linux-toradex.git/arch/s390/kernel/nmi.c, branch v4.9.90

s390/nmi: improve revalidation of fpu / vector registers

2016-08-29T09:05:03+00:00

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

s390/time: remove ETR support

2016-06-13T13:58:21+00:00

The External-Time-Reference (ETR) clock synchronization interface has
been superseded by Server-Time-Protocol (STP). Remove the outdated
ETR interface.

Signed-off-by: Martin Schwidefsky

s390/nmi: reduce size of percpu variable

2015-10-27T08:33:57+00:00

Change the flag fields within struct mcck_struct to simple bit fields
to reduce the size of the structure which is used as percpu variable.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/nmi: fix terminology

2015-10-27T08:33:56+00:00

According to the architecture registers are validated and not
revalidated. So change comments and functions names to match.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/nmi: remove casts

2015-10-27T08:33:55+00:00

Remove all the casts to and from the machine check interruption code.
This patch changes struct mci to a union, which contains an anonymous
structure with the already known bits and in addition an unsigned
long field, which contains the raw machine check interruption code.

This allows to simply assign and decoce the interruption code value
without the need for all those casts we had all the time.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/nmi: remove pointless error strings

2015-10-27T08:33:54+00:00

s390_handle_damage() has character string parameter which was used as
a pointer to verbose error message. The hope was (a lot of years ago)
when analyzing dumps that register R2 would still contain the pointer
and therefore it would be rather easy to tell what went wrong.

However gcc optimizes the strings away since a long time. And even if
it wouldn't it is necessary to have a close look at the machine check
interruption code to tell what's wrong.

So remove the pointless error strings.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/fpu: split fpu-internal.h into fpu internals, api, and type headers

2015-10-16T07:41:12+00:00

Split the API and FPU type definitions into separate header files
similar to "x86/fpu: Rename fpu-internal.h to fpu/internal.h" (78f7f1e54b).

The new header files and their meaning are:

asm/fpu/types.h:
	FPU related data types, needed for 'struct thread_struct' and
	'struct task_struct'.

asm/fpu/api.h:
	FPU related 'public' functions for other subsystems and device
	drivers.

asm/fpu/internal.h:
	FPU internal functions mainly used to convert
	FPU register contents in signal handling.

Signed-off-by: Hendrik Brueckner 
Signed-off-by: Martin Schwidefsky

s390/etr,stp: fix possible deadlock on machine check

2015-10-14T12:32:18+00:00

The first level machine check handler for etr and stp machine checks may
call queue_work() while in nmi context. This may deadlock e.g. if the
machine check happened when the interrupted context did hold a lock, that
also will be acquired by queue_work().
Therefore split etr and stp machine check handling into first and second
level handling. The second level handling will then issue the queue_work()
call in process context which avoids the potential deadlock.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/nmi: initialize control register 0 earlier

2015-08-19T08:40:38+00:00

Change machine_check_init() to an early_initcall(). This makes sure it will
be called before all other cpus are online and therfore saves us a lot of
pointless smp_call_function() calls.
The control register settings will be forwarded to the other cpus when they
will be brought online.

Signed-off-by: Heiko Carstens 
Reviewed-by: Hendrik Brueckner 
Signed-off-by: Martin Schwidefsky

s390/kernel: lazy restore fpu registers

2015-07-22T07:58:01+00:00

Improve the save and restore behavior of FPU register contents to use the
vector extension within the kernel.

The kernel does not use floating-point or vector registers and, therefore,
saving and restoring the FPU register contents are performed for handling
signals or switching processes only.  To prepare for using vector
instructions and vector registers within the kernel, enhance the save
behavior and implement a lazy restore at return to user space from a
system call or interrupt.

To implement the lazy restore, the save_fpu_regs() sets a CPU information
flag, CIF_FPU, to indicate that the FPU registers must be restored.
Saving and setting CIF_FPU is performed in an atomic fashion to be
interrupt-safe.  When the kernel wants to use the vector extension or
wants to change the FPU register state for a task during signal handling,
the save_fpu_regs() must be called first.  The CIF_FPU flag is also set at
process switch.  At return to user space, the FPU state is restored.  In
particular, the FPU state includes the floating-point or vector register
contents, as well as, vector-enablement and floating-point control.  The
FPU state restore and clearing CIF_FPU is also performed in an atomic
fashion.

For KVM, the restore of the FPU register state is performed when restoring
the general-purpose guest registers before the SIE instructions is started.
Because the path towards the SIE instruction is interruptible, the CIF_FPU
flag must be checked again right before going into SIE.  If set, the guest
registers must be reloaded again by re-entering the outer SIE loop.  This
is the same behavior as if the SIE critical section is interrupted.

Signed-off-by: Hendrik Brueckner 
Signed-off-by: Martin Schwidefsky