s390/mm,kvm: fix software dirty bits vs. kvm for old machines

For machines without enhanced supression on protection the software
dirty bit code forces the pte dirty bit and clears the page protection
bit in pgste_set_pte. This is done for all pte types, the check for
present ptes is missing. As a result swap ptes and other not-present
ptes can get corrupted.
Add a check for the _PAGE_PRESENT bit to pgste_set_pte before modifying
the pte value.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/dasd: check for availability of prefix command during format

The prefix command is used instead of a define extent to make use of
PAV alias devices during format. On some older storage servers the
prefix command may not be available and the IO request will fail.
Check for availability of prefix command and use define extent if
not available.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/compat,signal: fix return value of copy_siginfo_(to|from)_user32()

The return value of copy_siginfo_(to|from)_user32() gets passed to
user space, however we do not convert a positive return value from
copy_(to|from)_user to -EFAULT.
Therefore these functions (and the calling system calls) my incorrectly
return a positive number (bytes not copied) instead of -EFAULT.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/vmlogrdr: fix array access in vmlogrdr_open()

Fix check within vmlogrdr_open() if the minor address is not larger
than the number of array elements.

Found with "smatch":

drivers/s390/char/vmlogrdr.c:318 vmlogrdr_open() warn:
  buffer overflow 'sys_ser' 3 <= 3

Acked-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
s390/time: correct use of store clock fast

The result of the store-clock-fast (STCKF) instruction is a bit fuzzy.
It can happen that the value stored on one CPU is smaller than the value
stored on another CPU, although the order of the stores is the other
way around. This can cause deltas of get_tod_clock() values to become
negative when they should not be.

We need to be more careful with store-clock-fast, this patch partially
reverts git commit e4b7b4238e666682555461fa52eecd74652f36bb "time:
always use stckf instead of stck if available". The get_tod_clock()
function now uses the store-clock-extended (STCKE) instruction.
get_tod_clock_fast() can be used if the fuzziness of store-clock-fast
is acceptable e.g. for wait loops local to a CPU.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 fixes from Martin Schwidefsky:
 "Several last minute bug fixes.

  Two of them are on the larger side for rc7, the dasd format patch for
  older storage devices and the store-clock-fast patch where we have
  been to optimistic with an optimization"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/time: correct use of store clock fast
  s390/vmlogrdr: fix array access in vmlogrdr_open()
  s390/compat,signal: fix return value of copy_siginfo_(to|from)_user32()
  s390/dasd: check for availability of prefix command during format
  s390/mm,kvm: fix software dirty bits vs. kvm for old machines