linux.git/arch/powerpc/kernel/interrupt.c, branch v7.2-rc2

powerpc: Restore KUAP registers on syscall restart exit

2026-06-16T09:37:40+00:00

During a syscall restart, block KUAP so that pending interrupts can be
replayed. The original KUAP state is not restored before returning to
userspace, causing subsequent userspace accesses to fault and eventually
trigger bad_access_pkey(), crashing the kernel.

The original KUAP register values are already saved in
arch_enter_from_user_mode(). Restore them on the syscall restart exit
path before returning to userspace.

Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
Reported-by: Sayali Patil 
Closes: https://lore.kernel.org/linuxppc-dev/fcd11556-27ac-4cd7-8c77-50716dec6985@linux.ibm.com/
Signed-off-by: Mukesh Kumar Chaurasiya (IBM) 
Tested-by: Sayali Patil 
[Maddy: Added Closes tag]
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20260615162617.2861795-1-mkchauras@gmail.com

powerpc: Enable GENERIC_ENTRY feature

2026-05-20T01:27:14+00:00

Enable the generic IRQ entry/exit infrastructure on PowerPC by selecting
GENERIC_ENTRY and integrating the architecture-specific interrupt and
syscall handlers with the generic entry/exit APIs.

This change replaces PowerPC’s local interrupt entry/exit handling with
calls to the generic irqentry_* helpers, aligning the architecture with
the common kernel entry model. The macros that define interrupt, async,
and NMI handlers are updated to use irqentry_enter()/irqentry_exit()
and irqentry_nmi_enter()/irqentry_nmi_exit() where applicable also
convert the PowerPC syscall entry and exit paths to use the generic
entry/exit framework and integrating with the common syscall handling
routines.

Key updates include:
 - The architecture now selects GENERIC_ENTRY in Kconfig.
 - Replace interrupt_enter/exit_prepare() with arch_interrupt_* helpers.
 - Integrate irqentry_enter()/exit() in standard and async interrupt paths.
 - Integrate irqentry_nmi_enter()/exit() in NMI handlers.
 - Remove redundant irq_enter()/irq_exit() calls now handled generically.
 - Use irqentry_exit_cond_resched() for preemption checks.
 - interrupt.c and syscall.c are simplified to delegate context
   management and user exit handling to the generic entry path.
 - The new pt_regs field `exit_flags` introduced earlier is now used
   to carry per-syscall exit state flags (e.g. _TIF_RESTOREALL).
 - Remove unused code.

This change establishes the necessary wiring for PowerPC to use the
generic IRQ entry/exit framework while maintaining existing semantics.
This aligns PowerPC with the common entry code used by other
architectures and reduces duplicated logic around syscall tracing,
context tracking, and signal handling.

The performance benchmarks from perf bench basic syscall are below:

perf bench syscall usec/op (-ve is improvement)

| Syscall | Base        | test        | change % |
| ------- | ----------- | ----------- | -------- |
| basic   | 0.093543    | 0.093023    | -0.56    |
| execve  | 446.557781  | 450.107172  | +0.79    |
| fork    | 1142.204391 | 1156.377214 | +1.24    |
| getpgid | 0.097666    | 0.092677    | -5.11    |

perf bench syscall ops/sec (+ve is improvement)

| Syscall | Base     | New      | change % |
| ------- | -------- | -------- | -------- |
| basic   | 10690548 | 10750140 | +0.56    |
| execve  | 2239     | 2221     | -0.80    |
| fork    | 875      | 864      | -1.26    |
| getpgid | 10239026 | 10790324 | +5.38    |

IPI latency benchmark (-ve is improvement)

| Metric         | Base (ns)     | New (ns)      | % Change |
| -------------- | ------------- | ------------- | -------- |
| Dry run        | 583136.56     | 584136.35     | 0.17%    |
| Self IPI       | 4167393.42    | 4149093.90    | -0.44%   |
| Normal IPI     | 61769347.82   | 61753728.39   | -0.03%   |
| Broadcast IPI  | 2235584825.02 | 2227521401.45 | -0.36%   |
| Broadcast lock | 2164964433.31 | 2125658641.76 | -1.82%   |

Thats very close to performance earlier with arch specific handling.

Signed-off-by: Mukesh Kumar Chaurasiya 
Tested-by: Samir M 
Tested-by: David Gow 
Tested-by: Venkat Rao Bagalkote 
Reviewed-by: Shrikanth Hegde 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20260427122742.210074-8-mkchauras@gmail.com

powerpc: rename arch_irq_disabled_regs

2026-05-20T01:27:13+00:00

Rename arch_irq_disabled_regs() to regs_irqs_disabled() to align with the
naming used in the generic irqentry framework. This makes the function
available for use both in the PowerPC architecture code and in the
common entry/exit paths shared with other architectures.

This is a preparatory change for enabling the generic irqentry framework
on PowerPC.

Signed-off-by: Mukesh Kumar Chaurasiya 
Tested-by: Samir M 
Tested-by: David Gow 
Tested-by: Venkat Rao Bagalkote 
Reviewed-by: Shrikanth Hegde 
Reviewed-by: Jinjie Ruan 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20260427122742.210074-2-mkchauras@gmail.com

powerpc/32: Restore disabling of interrupts at interrupt/syscall exit

2025-12-22T12:55:07+00:00

Commit 2997876c4a1a ("powerpc/32: Restore clearing of MSR[RI] at
interrupt/syscall exit") delayed clearing of MSR[RI], but missed that
both MSR[RI] and MSR[EE] are cleared at the same time, so the commit
also delayed the disabling of interrupts, leading to unexpected
behaviour.

To fix that, mostly revert the blamed commit and restore the clearing
of MSR[RI] in interrupt_exit_kernel_prepare() instead. For 8xx it
implies adding a synchronising instruction after the mtspr in order to
make sure no instruction counter interrupt (used for perf events) will
fire just after clearing MSR[RI].

Reported-by: Christian Zigotzky 
Closes: https://lore.kernel.org/all/4d0bd05d-6158-1323-3509-744d3fbe8fc7@xenosoft.de/
Reported-by: Guenter Roeck 
Closes: https://lore.kernel.org/all/6b05eb1c-fdef-44e0-91a7-8286825e68f1@roeck-us.net/
Fixes: 2997876c4a1a ("powerpc/32: Restore clearing of MSR[RI] at interrupt/syscall exit")
Signed-off-by: Christophe Leroy (CS GROUP) 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/585ea521b2be99d293b539bbfae148366cfb3687.1766146895.git.chleroy@kernel.org

powerpc/32: Restore clearing of MSR[RI] at interrupt/syscall exit

2025-11-11T08:43:37+00:00

Commit 13799748b957 ("powerpc/64: use interrupt restart table to speed
up return from interrupt") removed the inconditional clearing of
MSR[RI] when returning from interrupt into kernel. But powerpc/32
doesn't implement interrupt restart table hence still need MSR[RI]
to be cleared.

It could be added back in interrupt_exit_kernel_prepare() but it is
easier and better to add it back in entry_32.S for following reasons:
- Writing to MSR must be followed by a synchronising instruction
- The smaller the non recoverable section is the better it is

So add a macro called clr_ri and use it in the three places that play
up with SRR0/SRR1. Use it just before another mtspr for synchronisation
to avoid having to add an isync.

Now that's done in entry_32.S, exit_must_hard_disable() can return
false for non book3s/64, taking into account that BOOKE doesn't have
MSR_RI.

Also add back blacklisting syscall_exit_finish for kprobe. This was
initially added by commit 7cdf44013885 ("powerpc/entry32: Blacklist
syscall exit points for kprobe.") then lost with
commit 6f76a01173cc ("powerpc/syscall: implement system call
entry/exit logic in C for PPC32").

Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
Fixes: 13799748b957 ("powerpc/64: use interrupt restart table to speed up return from interrupt")
Signed-off-by: Christophe Leroy 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/66d0ab070563ad460ed481328ab0887c27f21a2c.1757593807.git.christophe.leroy@csgroup.eu

powerpc: enable dynamic preemption

2025-04-16T17:00:22+00:00

Once the lazy preemption is supported, it would be desirable to change
the preemption models at runtime. So add support for dynamic preemption
using DYNAMIC_KEY.

::Tested lightly on Power10 LPAR
Performance numbers indicate that, preempt=none(no dynamic) and
preempt=none(dynamic) are close.

cat /sys/kernel/debug/sched/preempt
(none) voluntary full lazy
perf stat -e probe:__cond_resched -a sleep 1
 Performance counter stats for 'system wide':
             1,253      probe:__cond_resched

echo full > /sys/kernel/debug/sched/preempt
cat /sys/kernel/debug/sched/preempt
none voluntary (full) lazy
perf stat -e probe:__cond_resched -a sleep 1
 Performance counter stats for 'system wide':
                 0      probe:__cond_resched

Signed-off-by: Shrikanth Hegde 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20250210184334.567383-2-sshegde@linux.ibm.com

powerpc: Add preempt lazy support

2024-12-19T08:51:08+00:00

Define preempt lazy bit for Powerpc. Use bit 9 which is free and within
16 bit range of NEED_RESCHED, so compiler can issue single andi.

Since Powerpc doesn't use the generic entry/exit, add lazy check at exit
to user. CONFIG_PREEMPTION is defined for lazy/full/rt so use it for
return to kernel.

Ran a few benchmarks and db workload on Power10. Performance is close to
preempt=none/voluntary.

Since Powerpc systems can have large core count and large memory,
preempt lazy is going to be helpful in avoiding soft lockup issues.

Reviewed-by: Sebastian Andrzej Siewior 
Reviewed-by: Ankur Arora 
Signed-off-by: Shrikanth Hegde 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20241116192306.88217-2-sshegde@linux.ibm.com

treewide: context_tracking: Rename CONTEXT_* into CT_STATE_*

2024-07-29T02:03:10+00:00

Context tracking state related symbols currently use a mix of the
CONTEXT_ (e.g. CONTEXT_KERNEL) and CT_SATE_ (e.g. CT_STATE_MASK) prefixes.

Clean up the naming and make the ctx_state enum use the CT_STATE_ prefix.

Suggested-by: Frederic Weisbecker 
Signed-off-by: Valentin Schneider 
Acked-by: Frederic Weisbecker 
Acked-by: Thomas Gleixner 
Signed-off-by: Neeraj Upadhyay

rseq: Split out rseq.h from sched.h

2023-12-27T16:49:56+00:00

We're trying to get sched.h down to more or less just types only, not
code - rseq can live in its own header.

This helps us kill the dependency on preempt.h in sched.h.

Signed-off-by: Kent Overstreet

powerpc: Mark [h]ssr_valid accesses in check_return_regs_valid

2023-06-21T05:13:57+00:00

Checks to see if the [H]SRR registers have been clobbered by (soft)
NMI interrupts imply the possibility for a data race on the
[h]srr_valid entries in the PACA. Annotate accesses to these fields with
READ_ONCE, removing the need for the barrier.

The diagnostic can use plain-access reads and writes, but annotate with
data_race.

Signed-off-by: Rohan McLure 
Reported-by: Michael Ellerman 
Reviewed-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230510033117.1395895-5-rmclure@linux.ibm.com