linux.git/arch/s390/kernel/setup.c, branch v5.12

s390/setup: use memblock_free_late() to free old stack

2021-04-07T12:37:28+00:00

Use memblock_free_late() to free the old machine check stack to the
buddy allocator instead of leaking it.

Fixes: b61b1595124a ("s390: add stack for machine check handler")
Cc: Vasily Gorbik 
Acked-by: Sven Schnelle 
Signed-off-by: Heiko Carstens

s390: add stack for machine check handler

2021-02-13T16:17:53+00:00

The previous code used the normal kernel stack for machine checks.
This is problematic when a machine check interrupts a system call
or interrupt handler right at the beginning where registers are set up.

Assume system_call is interrupted at the first instruction and a machine
check is triggered. The machine check handler is called, checks the PSW
to see whether it is coming from user space, notices that it is already
in kernel mode but %r15 still contains the user space stack. This would
lead to a kernel crash.

There are basically two ways of fixing that: Either using the 'critical
cleanup' approach which compares the address in the PSW to see whether
it is already at a point where the stack has been set up, or use an extra
stack for the machine check handler.

For simplicity, we will go with the second approach and allocate an extra
stack. This adds some memory overhead for large systems, but usually large
system have plenty of memory so this isn't really a concern. But it keeps
the mchk stack setup simple and less error prone.

Fixes: 0b0ed657fe00 ("s390: remove critical section cleanup from entry.S")
Signed-off-by: Sven Schnelle 
Cc:  # v5.8+
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390: use WRITE_ONCE when re-allocating async stack

2021-02-13T16:17:53+00:00

The code does:

S390_lowcore.async_stack = new + STACK_INIT_OFFSET;

But the compiler is free to first assign one value and
add the other value later. If a IRQ would be coming in
between these two operations, it would run with an invalid
stack. Prevent this by using WRITE_ONCE.

Signed-off-by: Sven Schnelle 
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/delay: remove udelay_simple()

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

udelay_simple() callers can make use of the now simplified udelay()
implementation. No need to keep it.

Signed-off-by: Heiko Carstens

s390/mm: add support to allocate gigantic hugepages using CMA

2020-12-10T20:11:01+00:00

Commit cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages
using cma") added support for allocating gigantic hugepages using CMA,
by specifying the hugetlb_cma= kernel parameter, which will disable any
boot-time allocation of gigantic hugepages.

This patch enables that option also for s390.

Signed-off-by: Gerald Schaefer 
Signed-off-by: Heiko Carstens

s390: unify identity mapping limits handling

2020-11-20T18:19:10+00:00

Currently we have to consider too many different values which
in the end only affect identity mapping size. These are:
1. max_physmem_end - end of physical memory online or standby.
   Always <= end of the last online memory block (get_mem_detect_end()).
2. CONFIG_MAX_PHYSMEM_BITS - the maximum size of physical memory the
   kernel is able to support.
3. "mem=" kernel command line option which limits physical memory usage.
4. OLDMEM_BASE which is a kdump memory limit when the kernel is executed as
   crash kernel.
5. "hsa" size which is a memory limit when the kernel is executed during
   zfcp/nvme dump.

Through out kernel startup and run we juggle all those values at once
but that does not bring any amusement, only confusion and complexity.

Unify all those values to a single one we should really care, that is
our identity mapping size.

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

s390: make sure vmemmap is top region table entry aligned

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

Since commit 29d37e5b82f3 ("s390/protvirt: add ultravisor initialization")
vmax is adjusted to the ultravisor secure storage limit. This limit is
currently applied when 4-level paging is used. Later vmax is also used
to align vmemmap address to the top region table entry border. When vmax
is set to the ultravisor secure storage limit this is no longer the case.

Instead of changing vmax, make only MODULES_END be affected by the
secure storage limit, so that vmax stays intact for further vmemmap
address alignment.

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

s390/udelay: make it work for the early code

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

Currently udelay relies on working EXT interrupts handler, which is not
the case during early startup. In such cases udelay_simple() has to be
used instead.

To avoid mistakes of calling udelay too early, which could happen from
the common code as well - make udelay work for the early code by
introducing static branch and redirecting all udelay calls to
udelay_simple until EXT interrupts handler is fully initialized and
async stack is allocated.

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

Merge tag 's390-5.10-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2020-10-16T19:36:38+00:00

Pull s390 updates from Vasily Gorbik:

 - Remove address space overrides using set_fs()

 - Convert to generic vDSO

 - Convert to generic page table dumper

 - Add ARCH_HAS_DEBUG_WX support

 - Add leap seconds handling support

 - Add NVMe firmware-assisted kernel dump support

 - Extend NVMe boot support with memory clearing control and addition of
   kernel parameters

 - AP bus and zcrypt api code rework. Add adapter configure/deconfigure
   interface. Extend debug features. Add failure injection support

 - Add ECC secure private keys support

 - Add KASan support for running protected virtualization host with
   4-level paging

 - Utilize destroy page ultravisor call to speed up secure guests
   shutdown

 - Implement ioremap_wc() and ioremap_prot() with MIO in PCI code

 - Various checksum improvements

 - Other small various fixes and improvements all over the code

* tag 's390-5.10-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (85 commits)
  s390/uaccess: fix indentation
  s390/uaccess: add default cases for __put_user_fn()/__get_user_fn()
  s390/zcrypt: fix wrong format specifications
  s390/kprobes: move insn_page to text segment
  s390/sie: fix typo in SIGP code description
  s390/lib: fix kernel doc for memcmp()
  s390/zcrypt: Introduce Failure Injection feature
  s390/zcrypt: move ap_msg param one level up the call chain
  s390/ap/zcrypt: revisit ap and zcrypt error handling
  s390/ap: Support AP card SCLP config and deconfig operations
  s390/sclp: Add support for SCLP AP adapter config/deconfig
  s390/ap: add card/queue deconfig state
  s390/ap: add error response code field for ap queue devices
  s390/ap: split ap queue state machine state from device state
  s390/zcrypt: New config switch CONFIG_ZCRYPT_DEBUG
  s390/zcrypt: introduce msg tracking in zcrypt functions
  s390/startup: correct early pgm check info formatting
  s390: remove orphaned extern variables declarations
  s390/kasan: make sure int handler always run with DAT on
  s390/ipl: add support to control memory clearing for nvme re-IPL
  ...