linux.git/arch/s390/kernel/setup.c, branch v5.19

s390/archrandom: simplify back to earlier design and initialize earlier

2022-06-30T17:40:36+00:00

s390x appears to present two RNG interfaces:
- a "TRNG" that gathers entropy using some hardware function; and
- a "DRBG" that takes in a seed and expands it.

Previously, the TRNG was wired up to arch_get_random_{long,int}(), but
it was observed that this was being called really frequently, resulting
in high overhead. So it was changed to be wired up to arch_get_random_
seed_{long,int}(), which was a reasonable decision. Later on, the DRBG
was then wired up to arch_get_random_{long,int}(), with a complicated
buffer filling thread, to control overhead and rate.

Fortunately, none of the performance issues matter much now. The RNG
always attempts to use arch_get_random_seed_{long,int}() first, which
means a complicated implementation of arch_get_random_{long,int}() isn't
really valuable or useful to have around. And it's only used when
reseeding, which means it won't hit the high throughput complications
that were faced before.

So this commit returns to an earlier design of just calling the TRNG in
arch_get_random_seed_{long,int}(), and returning false in arch_get_
random_{long,int}().

Part of what makes the simplification possible is that the RNG now seeds
itself using the TRNG at bootup. But this only works if the TRNG is
detected early in boot, before random_init() is called. So this commit
also causes that check to happen in setup_arch().

Cc: stable@vger.kernel.org
Cc: Harald Freudenberger 
Cc: Ingo Franzki 
Cc: Juergen Christ 
Cc: Heiko Carstens 
Signed-off-by: Jason A. Donenfeld 
Link: https://lore.kernel.org/r/20220610222023.378448-1-Jason@zx2c4.com
Reviewed-by: Harald Freudenberger 
Acked-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev

s390/smp: sort out physical vs virtual CPU0 lowcore pointer

2022-04-25T11:54:13+00:00

SPX instruction called from set_prefix() expects physical
address of the lowcore to be installed, but instead the
virtual address is passed.

Note: this does not fix a bug currently, since virtual and
physical addresses are identical.

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

s390/maccess: rework absolute lowcore accessors

2022-03-27T20:18:39+00:00

Macro mem_assign_absolute() is able to access the whole memory, but
is only used and makes sense when updating the absolute lowcore.
Instead, introduce get_abs_lowcore() and put_abs_lowcore() macros
that limit access to absolute lowcore addresses only.

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

s390: raise minimum supported machine generation to z10

2022-03-10T14:58:17+00:00

Machine generations up to z9 (released in May 2006) have been officially
out of service for several years now (z9 end of service - January 31, 2019).
No distributions build kernels supporting those old machine generations
anymore, except Debian, which seems to pick the oldest supported
generation. The team supporting Debian on s390 has been notified about
the change.

Raising minimum supported machine generation to z10 helps to reduce
maintenance cost and effectively remove code, which is not getting
enough testing coverage due to lack of older hardware and distributions
support. Besides that this unblocks some optimization opportunities and
allows to use wider instruction set in asm files for future features
implementation. Due to this change spectre mitigation and usercopy
implementations could be drastically simplified and many newer instructions
could be converted from ".insn" encoding to instruction names.

Acked-by: Ilya Leoshkevich 
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/setup: preserve memory at OLDMEM_BASE and OLDMEM_SIZE

2022-03-01T19:41:28+00:00

We need to preserve the values at OLDMEM_BASE and OLDMEM_SIZE which are
used by zgetdump in case when kdump crashes. In that case zgetdump will
attempt to read OLDMEM_BASE and OLDMEM_SIZE in order to find out where
the memory range [0 - OLDMEM_SIZE] belonging to the production kernel is.

Fixes: f1a546947431 ("s390/setup: don't reserve memory that occupied decompressor's head")
Cc: stable@vger.kernel.org # 5.15+
Signed-off-by: Alexander Egorenkov 
Acked-by: Vasily Gorbik 
Signed-off-by: Vasily Gorbik

s390/nmi: disable interrupts on extended save area update

2021-12-16T18:58:07+00:00

Updating of the pointer to machine check extended save area
on the IPL CPU needs the lowcore protection to be disabled.
Disable interrupts while the protection is off to avoid
unnoticed writes to the lowcore.

Suggested-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens

s390/setup: re-arrange memblock setup

2021-11-16T11:29:19+00:00

- Avoid using ULONG_MAX in memblock_remove, it has no functional change
  but makes memblock_dbg output a range which makes sense.

- Actually finish memblock memory setup before doing amode31/cr/uv
  setup.

- Move memblock_dump_all() debug output after memblock memory setup is
  complete. This gives us final "memory" regions if they were trimmed
  due to addressing limits and still "physmem" regions as original info
  which came from mem_detect.

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

s390/setup: avoid using memblock_enforce_memory_limit

2021-11-16T11:29:18+00:00

There is a difference in how architectures treat "mem=" option. For some
that is an amount of online memory, for s390 and x86 this is the limiting
max address. Some memblock api like memblock_enforce_memory_limit()
take limit argument and explicitly treat it as the size of online memory,
and use __find_max_addr to convert it to an actual max address. Current
s390 usage:

memblock_enforce_memory_limit(memblock_end_of_DRAM());

yields different results depending on presence of memory holes (offline
memory blocks in between online memory). If there are no memory holes
limit == max_addr in memblock_enforce_memory_limit() and it does trim
online memory and reserved memory regions. With memory holes present it
actually does nothing.

Since we already use memblock_remove() explicitly to trim online memory
regions to potential limit (think mem=, kdump, addressing limits, etc.)
drop the usage of memblock_enforce_memory_limit() altogether. Trimming
reserved regions should not be required, since we now use
memblock_set_current_limit() to limit allocations and any explicit memory
reservations above the limit is an actual problem we should not hide.

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

s390/setup: avoid reserving memory above identity mapping

2021-11-16T11:29:18+00:00

Such reserved memory region, if not cleaned up later causes problems when
memblock_free_all() is called to release free pages to the buddy allocator
and those reserved regions are carried over to reserve_bootmem_region()
which marks the pages as PageReserved.

Instead use memblock_set_current_limit() to make sure memblock allocations
do not go over identity mapping (which could happen when "mem=" option
is used or during kdump).

Cc: stable@vger.kernel.org
Fixes: 73045a08cf55 ("s390: unify identity mapping limits handling")
Reported-by: Gerald Schaefer 
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik 
Signed-off-by: Heiko Carstens

Merge tag 's390-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2021-11-06T21:48:06+00:00

Pull s390 updates from Vasily Gorbik:

 - Add support for ftrace with direct call and ftrace direct call
   samples.

 - Add support for kernel command lines longer than current 896 bytes
   and make its length configurable.

 - Add support for BEAR enhancement facility to improve last breaking
   event instruction tracking.

 - Add kprobes sanity checks and testcases to prevent kprobe in the mid
   of an instruction.

 - Allow concurrent access to /dev/hwc for the CPUMF users.

 - Various ftrace / jump label improvements.

 - Convert unwinder tests to KUnit.

 - Add s390_iommu_aperture kernel parameter to tweak the limits on
   concurrently usable DMA mappings.

 - Add ap.useirq AP module option which can be used to disable interrupt
   use.

 - Add add_disk() error handling support to block device drivers.

 - Drop arch specific and use generic implementation of strlcpy and
   strrchr.

 - Several __pa/__va usages fixes.

 - Various cio, crypto, pci, kernel doc and other small fixes and
   improvements all over the code.

[ Merge fixup as per https://lore.kernel.org/all/YXAqZ%2FEszRisunQw@osiris/ ]

* tag 's390-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (63 commits)
  s390: make command line configurable
  s390: support command lines longer than 896 bytes
  s390/kexec_file: move kernel image size check
  s390/pci: add s390_iommu_aperture kernel parameter
  s390/spinlock: remove incorrect kernel doc indicator
  s390/string: use generic strlcpy
  s390/string: use generic strrchr
  s390/ap: function rework based on compiler warning
  s390/cio: make ccw_device_dma_* more robust
  s390/vfio-ap: s390/crypto: fix all kernel-doc warnings
  s390/hmcdrv: fix kernel doc comments
  s390/ap: new module option ap.useirq
  s390/cpumf: Allow multiple processes to access /dev/hwc
  s390/bitops: return true/false (not 1/0) from bool functions
  s390: add support for BEAR enhancement facility
  s390: introduce nospec_uses_trampoline()
  s390: rename last_break to pgm_last_break
  s390/ptrace: add last_break member to pt_regs
  s390/sclp: sort out physical vs virtual pointers usage
  s390/setup: convert start and end initrd pointers to virtual
  ...