linux.git/arch/s390/kernel, 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/pai: Fix multiple concurrent event installation

2022-06-23T15:24:00+00:00

Two different events such as pai_crypto/KM_AES_128/ and
pai_crypto/KM_AES_192/ can be installed multiple times on the same CPU
and the events are executed concurrently:

  # perf stat -e pai_crypto/KM_AES_128/  -C0 -a -- sleep 5 &
  # sleep 2
  # perf stat -e pai_crypto/KM_AES_192/ -C0 -a -- true

This results in the first event being installed two times with two seconds
delay. The kernel does install the second event after the first
event has been deleted and re-added, as can be seen in the traces:

 13:48:47.600350  paicrypt_start event 0x1007 (event KM_AES_128)
 13:48:49.599359  paicrypt_stop event 0x1007  (event KM_AES_128)
 13:48:49.599198  paicrypt_start event 0x1007
 13:48:49.599199  paicrypt_start event 0x1008
 13:48:49.599921  paicrypt_event_destroy event 0x1008
 13:48:52.601507  paicrypt_event_destroy event 0x1007

This is caused by functions event_sched_in() and event_sched_out() which
call the PMU's add() and start() functions on schedule_in and the PMU's
stop() and del() functions on schedule_out. This is correct for events
attached to processes.  The pai_crypto events are system-wide events
and not attached to processes.

Since the kernel common code can not be changed easily, fix this issue
and do not reset the event count value to zero each time the event is
added and started. Instead use a flag and zero the event count value
only when called immediately after the event has been initialized.
Therefore only the first invocation of the the event's add() function
initializes the event count value to zero. The following invocations
of the event's add() function leave the current event count value
untouched.

Fixes: 39d62336f5c1 ("s390/pai: add support for cryptography counters")

Reported-by: Sumanth Korikkar 
Signed-off-by: Thomas Richter 
Acked-by: Sumanth Korikkar 
Signed-off-by: Alexander Gordeev

s390/pai: Prevent invalid event number for pai_crypto PMU

2022-06-23T15:23:59+00:00

The pai_crypto PMU has to check the event number. It has to be in
the supported range. This is not the case, the lower limit is not
checked. Fix this and obey the lower limit.

Fixes: 39d62336f5c1 ("s390/pai: add support for cryptography counters")

Signed-off-by: Thomas Richter 
Suggested-by: Sumanth Korikkar 
Reviewed-by: Sumanth Korikkar 
Signed-off-by: Alexander Gordeev

s390/cpumf: Handle events cycles and instructions identical

2022-06-23T15:23:59+00:00

Events CPU_CYCLES and INSTRUCTIONS can be submitted with two different
perf_event attribute::type values:
 - PERF_TYPE_HARDWARE: when invoked via perf tool predefined events name
   cycles or cpu-cycles or instructions.
 - pmu->type: when invoked via perf tool event name cpu_cf/CPU_CYLCES/ or
   cpu_cf/INSTRUCTIONS/. This invocation also selects the PMU to which
   the event belongs.
Handle both type of invocations identical for events CPU_CYLCES and
INSTRUCTIONS. They address the same hardware.
The result is different when event modifier exclude_kernel is also set.
Invocation with event modifier for user space event counting fails.

Output before:

 # perf stat -e cpum_cf/cpu_cycles/u -- true

 Performance counter stats for 'true':

         cpum_cf/cpu_cycles/u

       0.000761033 seconds time elapsed

       0.000076000 seconds user
       0.000725000 seconds sys

 #

Output after:
 # perf stat -e cpum_cf/cpu_cycles/u -- true

 Performance counter stats for 'true':

           349,613      cpum_cf/cpu_cycles/u

       0.000844143 seconds time elapsed

       0.000079000 seconds user
       0.000800000 seconds sys
 #

Fixes: 6a82e23f45fe ("s390/cpumf: Adjust registration of s390 PMU device drivers")
Signed-off-by: Thomas Richter 
Acked-by: Sumanth Korikkar 
[agordeev@linux.ibm.com corrected commit ID of Fixes commit]
Signed-off-by: Alexander Gordeev

s390/crash: make copy_oldmem_page() return number of bytes copied

2022-06-23T15:23:30+00:00

Callback copy_oldmem_page() returns either error code or zero.
Instead, it should return the error code or number of bytes copied.

Fixes: df9694c7975f ("s390/dump: streamline oldmem copy functions")
Reviewed-by: Alexander Egorenkov 
Tested-by: Alexander Egorenkov 
Signed-off-by: Alexander Gordeev

s390/crash: add missing iterator advance in copy_oldmem_page()

2022-06-23T15:23:30+00:00

In case old memory was successfully copied the passed iterator
should be advanced as well. Currently copy_oldmem_page() is
always called with single-segment iterator. Should that ever
change - copy_oldmem_user and copy_oldmem_kernel() functions
would need a rework to deal with multi-segment iterators.

Fixes: 5d8de293c224 ("vmcore: convert copy_oldmem_page() to take an iov_iter")
Reviewed-by: Alexander Egorenkov 
Tested-by: Alexander Egorenkov 
Signed-off-by: Alexander Gordeev

Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-06-03T23:03:05+00:00

Pull kthread updates from Eric Biederman:
 "This updates init and user mode helper tasks to be ordinary user mode
  tasks.

  Commit 40966e316f86 ("kthread: Ensure struct kthread is present for
  all kthreads") caused init and the user mode helper threads that call
  kernel_execve to have struct kthread allocated for them. This struct
  kthread going away during execve in turned made a use after free of
  struct kthread possible.

  Here, commit 343f4c49f243 ("kthread: Don't allocate kthread_struct for
  init and umh") is enough to fix the use after free and is simple
  enough to be backportable.

  The rest of the changes pass struct kernel_clone_args to clean things
  up and cause the code to make sense.

  In making init and the user mode helpers tasks purely user mode tasks
  I ran into two complications. The function task_tick_numa was
  detecting tasks without an mm by testing for the presence of
  PF_KTHREAD. The initramfs code in populate_initrd_image was using
  flush_delayed_fput to ensuere the closing of all it's file descriptors
  was complete, and flush_delayed_fput does not work in a userspace
  thread.

  I have looked and looked and more complications and in my code review
  I have not found any, and neither has anyone else with the code
  sitting in linux-next"

* tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched: Update task_tick_numa to ignore tasks without an mm
  fork: Stop allowing kthreads to call execve
  fork: Explicitly set PF_KTHREAD
  init: Deal with the init process being a user mode process
  fork: Generalize PF_IO_WORKER handling
  fork: Explicity test for idle tasks in copy_thread
  fork: Pass struct kernel_clone_args into copy_thread
  kthread: Don't allocate kthread_struct for init and umh

Merge tag 's390-5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2022-06-03T20:57:50+00:00

Pull more s390 updates from Heiko Carstens:
 "Just a couple of small improvements, bug fixes and cleanups:

   - Add Eric Farman as maintainer for s390 virtio drivers.

   - Improve machine check handling, and avoid incorrectly injecting a
     machine check into a kvm guest.

   - Add cond_resched() call to gmap page table walker in order to avoid
     possible huge latencies. Also use non-quiesing sske instruction to
     speed up storage key handling.

   - Add __GFP_NORETRY to KEXEC_CONTROL_MEMORY_GFP so s390 behaves
     similar like common code.

   - Get sie control block address from correct stack slot in perf event
     code. This fixes potential random memory accesses.

   - Change uaccess code so that the exception handler sets the result
     of get_user() and __get_kernel_nofault() to zero in case of a
     fault. Until now this was done via input parameters for inline
     assemblies. Doing it via fault handling is what most or even all
     other architectures are doing.

   - Couple of other small cleanups and fixes"

* tag 's390-5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/stack: add union to reflect kvm stack slot usages
  s390/stack: merge empty stack frame slots
  s390/uaccess: whitespace cleanup
  s390/uaccess: use __noreturn instead of __attribute__((noreturn))
  s390/uaccess: use exception handler to zero result on get_user() failure
  s390/uaccess: use symbolic names for inline assembler operands
  s390/mcck: isolate SIE instruction when setting CIF_MCCK_GUEST flag
  s390/mm: use non-quiescing sske for KVM switch to keyed guest
  s390/gmap: voluntarily schedule during key setting
  MAINTAINERS: Update s390 virtio-ccw
  s390/kexec: add __GFP_NORETRY to KEXEC_CONTROL_MEMORY_GFP
  s390/Kconfig.debug: fix indentation
  s390/Kconfig: fix indentation
  s390/perf: obtain sie_block from the right address
  s390: generate register offsets into pt_regs automatically
  s390: simplify early program check handler
  s390/crypto: fix scatterwalk_unmap() callers in AES-GCM

s390/stack: add union to reflect kvm stack slot usages

2022-06-01T10:03:17+00:00

Add a union which describes how the empty stack slots are being used
by kvm and perf. This should help to avoid another bug like the one
which was fixed with commit c9bfb460c3e4 ("s390/perf: obtain sie_block
from the right address").

Reviewed-by: Nico Boehr 
Tested-by: Nico Boehr 
Signed-off-by: Heiko Carstens

s390/stack: merge empty stack frame slots

2022-06-01T10:03:17+00:00

Merge empty1 and empty2 arrays within the stack frame to one single
array. This is possible since with commit 42b01a553a56 ("s390: always
use the packed stack layout") the alternative stack frame layout is
gone.

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