linux.git/arch/s390/include/asm/processor.h, branch v5.12

s390: pass struct pt_regs instead of registers to syscalls

2021-01-19T11:29:27+00:00

Instead of fetching all registers from struct pt_regs and passing
them to the syscall wrappers, let the system call wrappers only
fetch the values really required.

Signed-off-by: Sven Schnelle 
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390: convert to generic entry

2021-01-19T11:29:26+00:00

This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.

There are a few special things on s390:

- PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't
  know about our PIF flags in exit_to_user_mode_loop().

- The old code had several ways to restart syscalls:

  a) PIF_SYSCALL_RESTART, which was only set during execve to force a
     restart after upgrading a process (usually qemu-kvm) to pgste page
     table extensions.

  b) PIF_SYSCALL, which is set by do_signal() to indicate that the
     current syscall should be restarted. This is changed so that
     do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use
     PIF_SYSCALL doesn't work with the generic code, and changing it
     to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART
     more unique.

- On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by
executing a svc instruction on the process stack which causes a fault.
While handling that fault the fault code sets PIF_SYSCALL to hand over
processing to the syscall code on exit to usermode.

The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets
a return value for a syscall. The s390x ptrace ABI uses r2 both for the
syscall number and return value, so ptrace cannot set the syscall number +
return value at the same time. The flag makes handling that a bit easier.
do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET
is set.

CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY.
CR1/7/13 will be checked both on kernel entry and exit to contain the
correct asces.

Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

s390/idle: merge enabled_wait() and arch_cpu_idle()

2020-12-16T13:55:49+00:00

The only caller of enabled_wait() besides arch_cpu_idle() was
udelay(). Since that call doesn't exist anymore, merge enabled_wait()
and arch_cpu_idle().

Signed-off-by: Heiko Carstens

s390/delay: simplify udelay

2020-12-16T13:55:49+00:00

udelay is implemented by using quite subtle details to make it
possible to load an idle psw and waiting for an interrupt even in irq
context or when interrupts are disabled. Also handling (or better: no
handling) of softirqs is taken into account.

All this is done to optimize for something which should in normal
circumstances never happen: calling udelay to busy wait. Therefore get
rid of the whole complexity and just busy loop like other
architectures are doing it also.

It could have been possible to use diag 0x44 instead of cpu_relax() in
the busy loop, however we have seen too many bad things happen with
diag 0x44 that it seems to be better to simply busy loop.

Also note that with this new implementation kernel preemption does
work when within the udelay loop. This did not work before.

To get a feeling what the former code optimizes for: IPL'ing a kernel
with 'defconfig' and afterwards compiling a kernel ends with a total
of zero udelay calls.

Signed-off-by: Heiko Carstens

s390/mm: remove set_fs / rework address space handling

2020-11-23T11:01:12+00:00

Remove set_fs support from s390. With doing this rework address space
handling and simplify it. As a result address spaces are now setup
like this:

CPU running in              | %cr1 ASCE | %cr7 ASCE | %cr13 ASCE
----------------------------|-----------|-----------|-----------
user space                  |  user     |  user     |  kernel
kernel, normal execution    |  kernel   |  user     |  kernel
kernel, kvm guest execution |  gmap     |  user     |  kernel

To achieve this the getcpu vdso syscall is removed in order to avoid
secondary address mode and a separate vdso address space in for user
space. The getcpu vdso syscall will be implemented differently with a
subsequent patch.

The kernel accesses user space always via secondary address space.
This happens in different ways:
- with mvcos in home space mode and directly read/write to secondary
  address space
- with mvcs/mvcp in primary space mode and copy from primary space to
  secondary space or vice versa
- with e.g. cs in secondary space mode and access secondary space

Switching translation modes happens with sacf before and after
instructions which access user space, like before.

Lazy handling of control register reloading is removed in the hope to
make everything simpler, but at the cost of making kernel entry and
exit a bit slower. That is: on kernel entry the primary asce is always
changed to contain the kernel asce, and on kernel exit the primary
asce is changed again so it contains the user asce.

In kernel mode there is only one exception to the primary asce: when
kvm guests are executed the primary asce contains the gmap asce (which
describes the guest address space). The primary asce is reset to
kernel asce whenever kvm guest execution is interrupted, so that this
doesn't has to be taken into account for any user space accesses.

Reviewed-by: Sven Schnelle 
Signed-off-by: Heiko Carstens

s390: remove unused s390_base_ext_handler

2020-11-09T10:20:58+00:00

s390_base_ext_handler_fn haven't been used since its introduction in
commit ab14de6c37fa ("[S390] Convert memory detection into C code.").

s390_base_ext_handler itself is currently falsely storing 16 registers
at __LC_SAVE_AREA_ASYNC rewriting several following lowcore values:
cpu_flags, return_psw, return_mcck_psw, sync_enter_timer and
async_enter_timer.

Besides that s390_base_ext_handler itself is only potentially hiding
EXT interrupts which should not have happen in the first place. Any
piece of code which requires EXT interrupts before fully functional
ext_int_handler is enabled has to do it on its own, like this is done
by sclp_early_cmd() which is doing EXT interrupts handling synchronously
in sclp_early_wait_irq().

With s390_base_ext_handler removed unexpected EXT interrupt leads
to disabled wait with the address 0x1b0 (__LC_EXT_NEW_PSW), which is
currently setup in the decompressor.

Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik 
Signed-off-by: Heiko Carstens

s390: remove critical section cleanup from entry.S

2020-05-28T10:21:54+00:00

The current code is rather complex and caused a lot of subtle
and hard to debug bugs in the past. Simplify the code by calling
the system_call handler with interrupts disabled, save
machine state, and re-enable them later.

This requires significant changes to the machine check handling code
as well. When the machine check interrupt arrived while being in kernel
mode the new code will signal pending machine checks with a SIGP external
call. When userspace was interrupted, the handler will switch to the
kernel stack and directly execute s390_handle_mcck().

Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

Merge tag 's390-5.7-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2020-04-04T16:45:50+00:00

Pull s390 updates from Vasily Gorbik:

- Update maintainers. Niklas Schnelle takes over zpci and Vineeth
Vijayan common io code.

- Extend cpuinfo to include topology information.

- Add new extended counters for IBM z15 and sampling buffer allocation
rework in perf code.

- Add control over zeroing out memory during system restart.

- CCA protected key block version 2 support and other
fixes/improvements in crypto code.

- Convert to new fallthrough; annotations.

- Replace zero-length arrays with flexible-arrays.

- QDIO debugfs and other small improvements.

- Drop 2-level paging support optimization for compat tasks. Varios mm
cleanups.

- Remove broken and unused hibernate / power management support.

- Remove fake numa support which does not bring any benefits.

- Exclude offline CPUs from CPU topology masks to be more consistent
with other architectures.

- Prevent last branching instruction address leaking to userspace.

- Other small various fixes and improvements all over the code.

* tag 's390-5.7-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (57 commits)
s390/mm: cleanup init_new_context() callback
s390/mm: cleanup virtual memory constants usage
s390/mm: remove page table downgrade support
s390/qdio: set qdio_irq->cdev at allocation time
s390/qdio: remove unused function declarations
s390/ccwgroup: remove pm support
s390/ap: remove power management code from ap bus and drivers
s390/zcrypt: use kvmalloc instead of kmalloc for 256k alloc
s390/mm: cleanup arch_get_unmapped_area() and friends
s390/ism: remove pm support
s390/cio: use fallthrough;
s390/vfio: use fallthrough;
s390/zcrypt: use fallthrough;
s390: use fallthrough;
s390/cpum_sf: Fix wrong page count in error message
s390/diag: fix display of diagnose call statistics
s390/ap: Remove ap device suspend and resume callbacks
s390/pci: Improve handling of unset UID
s390/pci: Fix zpci_alloc_domain() over allocation
s390/qdio: pass ISC as parameter to chsc_sadc()
...

s390/mm: cleanup virtual memory constants usage

2020-03-28T11:46:12+00:00

Remove duplicate definitions and consolidate usage
of virutal and address translation constants.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/mm: remove page table downgrade support

2020-03-28T11:46:12+00:00

This update consolidates page table handling code. Because
there are hardly any 31-bit binaries left we do not need to
optimize for that.

No extra efforts are needed to ensure that a compat task does
not map anything above 2GB. The TASK_SIZE limit for 31-bit
tasks is 2GB already and the generic code does check that a
resulting map address would not surpass that limit.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik