linux.git/arch/s390, branch v5.19

Merge tag 's390-5.19-7' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2022-07-26T17:03:53+00:00

Pull s390 fix from Alexander GordeevL

 - Prevent relatively slow PRNO TRNG random number operation from being
   called from interrupt context. That could for example cause some
   network loads to timeout.

* tag 's390-5.19-7' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/archrandom: prevent CPACF trng invocations in interrupt context

s390/archrandom: prevent CPACF trng invocations in interrupt context

2022-07-21T18:03:03+00:00

This patch slightly reworks the s390 arch_get_random_seed_{int,long}
implementation: Make sure the CPACF trng instruction is never
called in any interrupt context. This is done by adding an
additional condition in_task().

Justification:

There are some constrains to satisfy for the invocation of the
arch_get_random_seed_{int,long}() functions:
- They should provide good random data during kernel initialization.
- They should not be called in interrupt context as the TRNG
  instruction is relatively heavy weight and may for example
  make some network loads cause to timeout and buck.

However, it was not clear what kind of interrupt context is exactly
encountered during kernel init or network traffic eventually calling
arch_get_random_seed_long().

After some days of investigations it is clear that the s390
start_kernel function is not running in any interrupt context and
so the trng is called:

Jul 11 18:33:39 t35lp54 kernel:  [<00000001064e90ca>] arch_get_random_seed_long.part.0+0x32/0x70
Jul 11 18:33:39 t35lp54 kernel:  [<000000010715f246>] random_init+0xf6/0x238
Jul 11 18:33:39 t35lp54 kernel:  [<000000010712545c>] start_kernel+0x4a4/0x628
Jul 11 18:33:39 t35lp54 kernel:  [<000000010590402a>] startup_continue+0x2a/0x40

The condition in_task() is true and the CPACF trng provides random data
during kernel startup.

The network traffic however, is more difficult. A typical call stack
looks like this:

Jul 06 17:37:07 t35lp54 kernel:  [<000000008b5600fc>] extract_entropy.constprop.0+0x23c/0x240
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b560136>] crng_reseed+0x36/0xd8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b5604b8>] crng_make_state+0x78/0x340
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b5607e0>] _get_random_bytes+0x60/0xf8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b56108a>] get_random_u32+0xda/0x248
Jul 06 17:37:07 t35lp54 kernel:  [<000000008aefe7a8>] kfence_guarded_alloc+0x48/0x4b8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008aeff35e>] __kfence_alloc+0x18e/0x1b8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008aef7f10>] __kmalloc_node_track_caller+0x368/0x4d8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b611eac>] kmalloc_reserve+0x44/0xa0
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b611f98>] __alloc_skb+0x90/0x178
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b6120dc>] __napi_alloc_skb+0x5c/0x118
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b8f06b4>] qeth_extract_skb+0x13c/0x680
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b8f6526>] qeth_poll+0x256/0x3f8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b63d76e>] __napi_poll.constprop.0+0x46/0x2f8
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b63dbec>] net_rx_action+0x1cc/0x408
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b937302>] __do_softirq+0x132/0x6b0
Jul 06 17:37:07 t35lp54 kernel:  [<000000008abf46ce>] __irq_exit_rcu+0x13e/0x170
Jul 06 17:37:07 t35lp54 kernel:  [<000000008abf531a>] irq_exit_rcu+0x22/0x50
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b922506>] do_io_irq+0xe6/0x198
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b935826>] io_int_handler+0xd6/0x110
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b9358a6>] psw_idle_exit+0x0/0xa
Jul 06 17:37:07 t35lp54 kernel: ([<000000008ab9c59a>] arch_cpu_idle+0x52/0xe0)
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b933cfe>] default_idle_call+0x6e/0xd0
Jul 06 17:37:07 t35lp54 kernel:  [<000000008ac59f4e>] do_idle+0xf6/0x1b0
Jul 06 17:37:07 t35lp54 kernel:  [<000000008ac5a28e>] cpu_startup_entry+0x36/0x40
Jul 06 17:37:07 t35lp54 kernel:  [<000000008abb0d90>] smp_start_secondary+0x148/0x158
Jul 06 17:37:07 t35lp54 kernel:  [<000000008b935b9e>] restart_int_handler+0x6e/0x90

which confirms that the call is in softirq context. So in_task() covers exactly
the cases where we want to have CPACF trng called: not in nmi, not in hard irq,
not in soft irq but in normal task context and during kernel init.

Signed-off-by: Harald Freudenberger 
Acked-by: Jason A. Donenfeld 
Reviewed-by: Juergen Christ 
Link: https://lore.kernel.org/r/20220713131721.257907-1-freude@linux.ibm.com
Fixes: e4f74400308c ("s390/archrandom: simplify back to earlier design and initialize earlier")
[agordeev@linux.ibm.com changed desc, added Fixes and Link, removed -stable]
Signed-off-by: Alexander Gordeev

mmu_gather: Remove per arch tlb_{start,end}_vma()

2022-07-21T17:50:13+00:00

Scattered across the archs are 3 basic forms of tlb_{start,end}_vma().
Provide two new MMU_GATHER_knobs to enumerate them and remove the per
arch tlb_{start,end}_vma() implementations.

 - MMU_GATHER_NO_FLUSH_CACHE indicates the arch has flush_cache_range()
   but does *NOT* want to call it for each VMA.

 - MMU_GATHER_MERGE_VMAS indicates the arch wants to merge the
   invalidate across multiple VMAs if possible.

With these it is possible to capture the three forms:

  1) empty stubs;
     select MMU_GATHER_NO_FLUSH_CACHE and MMU_GATHER_MERGE_VMAS

  2) start: flush_cache_range(), end: empty;
     select MMU_GATHER_MERGE_VMAS

  3) start: flush_cache_range(), end: flush_tlb_range();
     default

Obviously, if the architecture does not have flush_cache_range() then
it also doesn't need to select MMU_GATHER_NO_FLUSH_CACHE.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Will Deacon 
Cc: David Miller 
Signed-off-by: Linus Torvalds

s390/nospec: remove unneeded header includes

2022-07-13T13:21:55+00:00

Commit 4efd417f298b ("s390: raise minimum supported machine generation
to z10") removed the usage of alternatives and lowcore in expolines
macros. Remove unneeded header includes as well.

With that, expoline.S doesn't require asm-offsets.h and
expoline_prepare target dependency could be removed.

Tested-by: Joe Lawrence 
Link: https://lore.kernel.org/r/patch-2.thread-d13b6c.git-d13b6c96fb5f.your-ad-here.call-01656331067-ext-4899@work.hours
Signed-off-by: Vasily Gorbik 
Signed-off-by: Alexander Gordeev

s390/nospec: build expoline.o for modules_prepare target

2022-07-13T13:21:55+00:00

When CONFIG_EXPOLINE_EXTERN is used expoline thunks are generated
from arch/s390/lib/expoline.S and postlinked into every module.
This is also true for external modules. Add expoline.o build to
the modules_prepare target.

Fixes: 1d2ad084800e ("s390/nospec: add an option to use thunk-extern")
Reported-by: Joe Lawrence 
Tested-by: Sumanth Korikkar 
Acked-by: Sumanth Korikkar 
Tested-by: C. Erastus Toe 
Tested-by: Joe Lawrence 
Link: https://lore.kernel.org/r/patch-1.thread-d13b6c.git-a2387a74dc49.your-ad-here.call-01656331067-ext-4899@work.hours
Signed-off-by: Vasily Gorbik 
Signed-off-by: Alexander Gordeev

s390/qdio: Fix spelling mistake

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

Change 'defineable' to 'definable'.
Change 'paramater' to 'parameter'.

Signed-off-by: Zhang Jiaming 
Reviewed-by: Benjamin Block 
Link: https://lore.kernel.org/r/20220623060543.12870-1-jiaming@nfschina.com
Signed-off-by: Alexander Gordeev

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/purgatory: remove duplicated build rule of kexec-purgatory.o

2022-06-30T12:18:16+00:00

This is equivalent to the pattern rule in scripts/Makefile.build.

Having the dependency on $(obj)/purgatory.ro is enough.

Signed-off-by: Masahiro Yamada 
Link: https://lore.kernel.org/r/20220613170902.1775211-3-masahiroy@kernel.org
Signed-off-by: Alexander Gordeev

s390/purgatory: hard-code obj-y in Makefile

2022-06-30T12:18:15+00:00

The purgatory/ directory is entirely guarded in arch/s390/Kbuild.
CONFIG_ARCH_HAS_KEXEC_PURGATORY is bool type.

$(CONFIG_ARCH_HAS_KEXEC_PURGATORY) is always 'y' when Kbuild visits
this Makefile for building.

Signed-off-by: Masahiro Yamada 
Link: https://lore.kernel.org/r/20220613170902.1775211-2-masahiroy@kernel.org
Signed-off-by: Alexander Gordeev

s390: remove unneeded 'select BUILD_BIN2C'

2022-06-30T12:18:15+00:00

Since commit 4c0f032d4963 ("s390/purgatory: Omit use of bin2c"),
s390 builds the purgatory without using bin2c.

Remove 'select BUILD_BIN2C' to avoid the unneeded build of bin2c.

Fixes: 4c0f032d4963 ("s390/purgatory: Omit use of bin2c")
Signed-off-by: Masahiro Yamada 
Link: https://lore.kernel.org/r/20220613170902.1775211-1-masahiroy@kernel.org
Signed-off-by: Alexander Gordeev