smp: Consolidate smp_prepare_boot_cpu()

There is no point in having seven architectures implementing the same empty
stub.

Provide a weak function in the init code and remove the stubs.

This also allows to utilize the function on UP which is required to
sanitize the per CPU handling on X86 UP.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240304005104.567671691@linutronix.de

openrisc: Add missing prototypes for assembly called fnctions

These functions are all called from assembly files so there is no need
for a prototype in a header file, but when compiling with W=1 enabling
-Wmissing-prototypes the compiler warns:

arch/openrisc/kernel/ptrace.c:191:17: error: no previous prototype for 'do_syscall_trace_enter' [-Werror=missing-prototypes]
arch/openrisc/kernel/ptrace.c:210:17: error: no previous prototype for 'do_syscall_trace_leave' [-Werror=missing-prototypes]
arch/openrisc/kernel/signal.c:293:1: error: no previous prototype for 'do_work_pending' [-Werror=missing-prototypes]
arch/openrisc/kernel/signal.c:68:17: error: no previous prototype for '_sys_rt_sigreturn' [-Werror=missing-prototypes]
arch/openrisc/kernel/time.c:111:25: error: no previous prototype for 'timer_interrupt' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:239:17: error: no previous prototype for 'unhandled_exception' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:246:17: error: no previous prototype for 'do_fpe_trap' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:268:17: error: no previous prototype for 'do_trap' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:273:17: error: no previous prototype for 'do_unaligned_access' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:286:17: error: no previous prototype for 'do_bus_fault' [-Werror=missing-prototypes]
arch/openrisc/kernel/traps.c:462:17: error: no previous prototype for 'do_illegal_instruction' [-Werror=missing-prototypes]
arch/openrisc/mm/fault.c:44:17: error: no previous prototype for 'do_page_fault' [-Werror=missing-prototypes]

Since these are not needed in header files, fix these by adding
prototypes to the top of the respective C files.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/linux-kernel/20230810141947.1236730-17-arnd@kernel.org/
Signed-off-by: Stafford Horne <shorne@gmail.com>

treewide: Trace IPIs sent via smp_send_reschedule()

To be able to trace invocations of smp_send_reschedule(), rename the
arch-specific definitions of it to arch_smp_send_reschedule() and wrap it
into an smp_send_reschedule() that contains a tracepoint.

Changes to include the declaration of the tracepoint were driven by the
following coccinelle script:

@func_use@
@@
smp_send_reschedule(...);

@include@
@@
#include <trace/events/ipi.h>

@no_include depends on func_use && !include@
@@
#include <...>
+
+ #include <trace/events/ipi.h>

[csky bits]
[riscv bits]
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230307143558.294354-6-vschneid@redhat.com

profile: setup_profiling_timer() is moslty not implemented

The setup_profiling_timer() is mostly un-implemented by many
architectures. In many places it isn't guarded by CONFIG_PROFILE which is
needed for it to be used. Make it a weak symbol in kernel/profile.c and
remove the 'return -EINVAL' implementations from the kenrel.

There are a couple of architectures which do return 0 from the
setup_profiling_timer() function but they don't seem to do anything else
with it. To keep the /proc compatibility for now, leave these for a
future update or removal.

On ARM, this fixes the following sparse warning:
arch/arm/kernel/smp.c:793:5: warning: symbol 'setup_profiling_timer' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220721195509.418205-1-ben-linux@fluff.org
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

openrisc: fix SMP tlb flush NULL pointer dereference

Throughout the OpenRISC kernel port VMA is passed as NULL when flushing
kernel tlb entries. Somehow this was missed when I was testing
c28b27416da9 ("openrisc: Implement proper SMP tlb flushing") and now the
SMP kernel fails to completely boot.

In OpenRISC VMA is used only to determine which cores need to have their
TLB entries flushed.

This patch updates the logic to flush tlbs on all cores when the VMA is
passed as NULL. Also, we update places VMA is passed as NULL to use
flush_tlb_kernel_range instead. Now, the only place VMA is passed as
NULL is in the implementation of flush_tlb_kernel_range.

Fixes: c28b27416da9 ("openrisc: Implement proper SMP tlb flushing")
Reported-by: Jan Henrik Weinstock <jan.weinstock@rwth-aachen.de>
Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: Use of_get_cpu_hwid()

Replace open coded parsing of CPU nodes' 'reg' property with
of_get_cpu_hwid().

Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: openrisc@lists.librecores.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Link: https://lore.kernel.org/r/20211006164332.1981454-7-robh@kernel.org

sched/core: Initialize the idle task with preemption disabled

As pointed out by commit

de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread")

init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.

As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().

Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().

Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().

Secondary startups were patched via coccinelle:

@begone@
@@

-preempt_disable();
...
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com

openrisc: Use devicetree to determine present cpus

Use the device tree to determine the present cpus instead of assuming
all CONFIG_NRCPUS are actually present in the system.

Signed-off-by: Jan Henrik Weinstock <jan.weinstock@rwth-aachen.de>
[shorne: Squashed 2 email commits and added summary from email]
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: Implement proper SMP tlb flushing

Up until now when flushing pages from the TLB on SMP OpenRISC was always
resorting to flush the entire TLB on all CPUs. This patch adds the
mechanics for flushing specific ranges and pages based on the usage.

The function switch_mm is updated to account for cpu usage by updating
mm_struct's cpumask. This is used in the SMP flush routines.

This mostly follows the riscv implementation.

Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: use mmgrab

Mmgrab was introduced in commit f1f1007644ff ("mm: add new mmgrab()
helper") and most of the kernel was updated to use it. Update a
remaining file.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

<smpl>
@@ expression e; @@
- atomic_inc(&e->mm_count);
+ mmgrab(e);
</smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Stafford Horne <shorne@gmail.com>
[shorne: Added missing sched/mm.h include]

openrisc: fix possible deadlock scenario during timer sync

OpenRISC borrows its timer sync logic from MIPS, Matt helped to review
the OpenRISC implementation and noted that we may suffer the same
deadlock case that MIPS has faced. The case being:

"the MIPS timer synchronization code contained the possibility of
deadlock. If you mark a CPU online before it goes into the synchronize
loop, then the boot CPU can schedule a different thread and send IPIs to
all "online" CPUs. It gets stuck waiting for the secondary to ack it's
IPI, since this secondary CPU has not enabled IRQs yet, and is stuck
waiting for the master to synchronise with it. The system then
deadlocks."

Fix this by moving set_cpu_online() to after timer sync.

Reported-by: Matt Redfearn <matt.redfearn@mips.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: add tick timer multi-core sync logic

In case timers are not in sync when cpus start (i.e. hot plug / offset
resets) we need to synchronize the secondary cpus internal timer with
the main cpu. This is needed as in OpenRISC SMP there is only one
clocksource registered which reads from the same ttcr register on each
cpu.

This synchronization routine heavily borrows from mips implementation that
does something similar.

Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: add cacheflush support to fix icache aliasing

On OpenRISC the icache does not snoop data stores. This can cause
aliasing as reported by Jan. This patch fixes the issue to ensure icache
is properly synchronized when code is written to memory. It supports both
SMP and UP flushing.

This supports dcache flush as well for architectures that do not support
write-through caches; most OpenRISC implementations do implement
write-through cache however. Dcache flushes are done only on a single
core as OpenRISC dcaches all support snooping of bus stores.

Signed-off-by: Jan Henrik Weinstock <jan.weinstock@ice.rwth-aachen.de>
[shorne@gmail.com: Squashed patches and wrote commit message]
Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: sleep instead of spin on secondary wait

Currently we do a spin on secondary cpus when waiting to boot. This
theoretically causes issues with power consumption and does cause issues
with qemu cycle burning (it starves cpu 0 from actually being able to
boot.)

This change puts each secondary cpu to sleep if they have a power
management unit, then signals them to wake via IPI when its time to boot.
If the cpus have no power management unit they will loop as before.

Note: The wakeup IPI requires a special interrupt handler as on secondary
cpu's the interrupt infrastructure is not yet established. This
interrupt handler is set and reset by updating SPR_EVBAR.

Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: fix initial preempt state for secondary cpu tasks

During SMP testing we were getting the below warning after booting the
secondary cpu:

[ 0.060000] BUG: scheduling while atomic: swapper/1/0/0x00000000

This change follows similar patterns from other architectures to start
the schduler with preempt disabled.

Signed-off-by: Stafford Horne <shorne@gmail.com>

openrisc: initial SMP support

This patch introduces the SMP support for the OpenRISC architecture.
The SMP architecture requires cores which have multi-core features which
have been introduced a few years back including:

- New SPRS SPR_COREID SPR_NUMCORES
- Shadow SPRs
- Atomic Instructions
- Cache Coherency
- A wired in IPI controller

This patch adds all of the SMP specific changes to core infrastructure,
it looks big but it needs to go all together as its hard to split this
one up.

Boot loader spinning of second cpu is not supported yet, it's assumed
that Linux is booted straight after cpu reset.

The bulk of these changes are trivial changes to refactor to use per cpu
data structures throughout. The addition of the smp.c and changes in
time.c are the changes. Some specific notes:

MM changes
----------
The reason why this is created as an array, and not with DEFINE_PER_CPU
is that doing it this way, we'll save a load in the tlb-miss handler
(the load from __per_cpu_offset).

TLB Flush
---------
The SMP implementation of flush_tlb_* works by sending out a
function-call IPI to all the non-local cpus by using the generic
on_each_cpu() function.

Currently, all flush_tlb_* functions will result in a flush_tlb_all(),
which has always been the behaviour in the UP case.

CPU INFO
--------
This creates a per cpu cpuinfo struct and fills it out accordingly for
each activated cpu. show_cpuinfo is also updated to reflect new version
information in later versions of the spec.

SMP API
-------
This imitates the arm64 implementation by having a smp_cross_call
callback that can be set by set_smp_cross_call to initiate an IPI and a
handle_IPI function that is expected to be called from an IPI irqchip
driver.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
[shorne@gmail.com: added cpu stop, checkpatch fixes, wrote commit message]
Signed-off-by: Stafford Horne <shorne@gmail.com>