linux.git/arch/s390/kernel/setup.c, branch v4.15

s390: kernel: add SPDX identifiers to the remaining files

2017-11-24T14:37:12+00:00

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the arch/s390/kernel/ files with the correct SPDX license
identifier based on the license text in the file itself.  The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Arnaldo Carvalho de Melo 
Cc: Alexander Shishkin 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Thomas Gleixner 
Cc: Kate Stewart 
Cc: Philippe Ombredanne 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Martin Schwidefsky

s390: simplify transactional execution elf hwcap handling

2017-11-09T15:54:30+00:00

Just use MACHINE_HAS_TE to decide if HWCAP_S390_TE needs
to be added to elf_hwcap.

Suggested-by: Dan Horák 
Reviewed-by: Christian Borntraeger 
Reviewed-by: Hendrik Brueckner 
Signed-off-by: Heiko Carstens

s390/virtio: remove unused header file kvm_virtio.h

2017-11-09T14:54:07+00:00

With commit 7fb2b2d51244 ("s390/virtio: remove the old KVM virtio
transport") the pre-ccw virtio transport for s390 was removed. To
complete the removal the uapi header file that contains the related data
structures must also be removed.

Signed-off-by: Christian Borntraeger 
Signed-off-by: Heiko Carstens

s390/nmi: allocation of the extended save area

2017-10-19T15:07:39+00:00

The machine check extended save area is needed to store the vector
registers and the guarded storage control block when a CPU is
interrupted by a machine check.

Move the slab cache allocation of the full save area to nmi.c,
for early boot use a static __initdata block.

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

s390/vdso: move boot_vdso_data to vdso.c

2017-10-18T12:11:36+00:00

The boot_vdso_data variable is related to the vdso code, the magic of the
initial vdso area for the early boot and the replacement of it in vdso_init
should all be put into vdso.c.

Signed-off-by: Martin Schwidefsky

s390: introduce CPU alternatives

2017-10-18T12:11:29+00:00

Implement CPU alternatives, which allows to optionally patch newer
instructions at runtime, based on CPU facilities availability.

A new kernel boot parameter "noaltinstr" disables patching.

Current implementation is derived from x86 alternatives. Although
ideal instructions padding (when altinstr is longer then oldinstr)
is added at compile time, and no oldinstr nops optimization has to be
done at runtime. Also couple of compile time sanity checks are done:
1. oldinstr and altinstr must be <= 254 bytes long,
2. oldinstr and altinstr must not have an odd length.

alternative(oldinstr, altinstr, facility);
alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2);

Both compile time and runtime padding consists of either 6/4/2 bytes nop
or a jump (brcl) + 2 bytes nop filler if padding is longer then 6 bytes.

.altinstructions and .altinstr_replacement sections are part of
__init_begin : __init_end region and are freed after initialization.

Signed-off-by: Vasily Gorbik 
Signed-off-by: Martin Schwidefsky

s390/spinlock: introduce spinlock wait queueing

2017-09-28T05:29:44+00:00

The queued spinlock code for s390 follows the principles of the common
code qspinlock implementation but with a few notable differences.

The format of the spinlock_t locking word differs, s390 needs to store
the logical CPU number of the lock holder in the spinlock_t to be able
to use the diagnose 9c directed yield hypervisor call.

The inline code sequences for spin_lock and spin_unlock are nice and
short. The inline portion of a spin_lock now typically looks like this:

	lhi	%r0,0			# 0 indicates an empty lock
	l	%r1,0x3a0		# CPU number + 1 from lowcore
	cs	%r0,%r1,	# lock operation
	jnz	call_wait		# on failure call wait function
locked:
	...
call_wait:
	la	%r2,
	brasl	%r14,arch_spin_lock_wait
	j	locked

A spin_unlock is as simple as before:

	lhi	%r0,0
	sth	%r0,2(%r2)		# unlock operation

After a CPU has queued itself it may not enable interrupts again for the
arch_spin_lock_flags() variant. The arch_spin_lock_wait_flags wait function
is removed.

To improve performance the code implements opportunistic lock stealing.
If the wait function finds a spinlock_t that indicates that the lock is
free but there are queued waiters, the CPU may steal the lock up to three
times without queueing itself. The lock stealing update the steal counter
in the lock word to prevent more than 3 steals. The counter is reset at
the time the CPU next in the queue successfully takes the lock.

While the queued spinlocks improve performance in a system with dedicated
CPUs, in a virtualized environment with continuously overcommitted CPUs
the queued spinlocks can have a negative effect on performance. This
is due to the fact that a queued CPU that is preempted by the hypervisor
will block the queue at some point even without holding the lock. With
the classic spinlock it does not matter if a CPU is preempted that waits
for the lock. Therefore use the queued spinlock code only if the system
runs with dedicated CPUs and fall back to classic spinlocks when running
with shared CPUs.

Signed-off-by: Martin Schwidefsky

s390/vmcp: make use of contiguous memory allocator

2017-08-09T13:09:35+00:00

If memory is fragmented it is unlikely that large order memory
allocations succeed. This has been an issue with the vmcp device
driver since a long time, since it requires large physical contiguous
memory ares for large responses.

To hopefully resolve this issue make use of the contiguous memory
allocator (cma). This patch adds a vmcp specific vmcp cma area with a
default size of 4MB. The size can be changed either via the
VMCP_CMA_SIZE config option at compile time or with the "vmcp_cma"
kernel parameter (e.g. "vmcp_cma=16m").

For any vmcp response buffers larger than 16k memory from the cma area
will be allocated. If such an allocation fails, there is a fallback to
the buddy allocator.

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

s390: add support for IBM z14 machines

2017-07-26T06:25:15+00:00

Add detection for machine type 0x3906 and set the ELF platform name
to z14. Add the miscellaneous-instruction-extension 2 facility to
the list of facilities for z14.

And allow to generate code that only runs on a z14 machine.

Signed-off-by: Martin Schwidefsky

s390/time: add support for the TOD clock epoch extension

2017-07-26T06:25:14+00:00

The TOD epoch extension adds 8 epoch bits to the TOD clock to provide
a continuous clock after 2042/09/17. The store-clock-extended (STCKE)
instruction will store the epoch index in the first byte of the
16 bytes stored by the instruction. The read_boot_clock64 and the
read_presistent_clock64 functions need to take the additional bits
into account to give the correct result after 2042/09/17.

The clock-comparator register will stay 64 bit wide. The comparison
of the clock-comparator with the TOD clock is limited to bytes
1 to 8 of the extended TOD format. To deal with the overflow problem
due to an epoch change the clock-comparator sign control in CR0 can
be used to switch the comparison of the 64-bit TOD clock with the
clock-comparator to a signed comparison.

The decision between the signed vs. unsigned clock-comparator
comparisons is done at boot time. Only if the TOD clock is in the
second half of a 142 year epoch the signed comparison is used.
This solves the epoch overflow issue as long as the machine is
booted at least once in an epoch.

Signed-off-by: Martin Schwidefsky