On Tue, May 13, 2025 at 03:17:00PM -0700, Shakeel Butt wrote:
> > IIRC Power64 has issues here, 'funnily' their local_t is NMI safe.
> > Perhaps we could do the same for their this_cpu_*(), but ideally someone
> > with actual power hardware should do this ;-)
> >
>
> Is CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS the right config to
> differentiate between such archs? I see Power64 does not have that
> enabled.
> > There is no config symbol for this presently.
>
> Hmm what about CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS?
Hmm, I didn't know about that one, and it escaped my grep yesterday.
Anyway, PPC is fixable, just not sure its worth it for them.
> >
> > > - (if the above leaves any 64bit arch) its 64bit atomics implementation is safe
> >
> > True, only because HPPA does not in fact have NMIs.
>
> What is HPPA?
arch/parisc the worst 64bit arch ever.
They saw sparc32-smp and thought that was a great idea, or something
along those lines. Both are quite terrible. Sparc64 realized the mistake
and fixed it -- it has cmpxchg.
Nick, is this something that's useful for you guys?
---
diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
index ecf5ac70cfae..aa188db68ef5 100644
--- a/arch/powerpc/include/asm/percpu.h
+++ b/arch/powerpc/include/asm/percpu.h
@@ -25,6 +25,11 @@ DECLARE_STATIC_KEY_FALSE(__percpu_first_chunk_is_paged);
#define percpu_first_chunk_is_paged false
#endif
+#ifdef CONFIG_PPC_BOOK3S_64
+#define __pcpu_local_irq_save(f) powerpc_local_irq_pmu_save(f)
+#define __pcpu_local_irq_restore(s) powerpc_local_irq_pmu_restore(f)
+#endif
+
#include <asm-generic/percpu.h>
#include <asm/paca.h>
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 02aeca21479a..5c8376588dfb 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -75,6 +75,11 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_ATTRIBUTES
#endif
+#ifndef __pcpu_local_irq_save
+#define __pcpu_local_irq_save(x) raw_local_irq_save(x)
+#define __pcpu_local_irq_restore(x) raw_local_irq_restore(x)
+#endif
+
#define raw_cpu_generic_read(pcp) \
({ \
*raw_cpu_ptr(&(pcp)); \
@@ -146,9 +151,9 @@ do { \
({ \
TYPEOF_UNQUAL(pcp) ___ret; \
unsigned long ___flags; \
- raw_local_irq_save(___flags); \
+ __pcpu_local_irq_save(___flags); \
___ret = raw_cpu_generic_read(pcp); \
- raw_local_irq_restore(___flags); \
+ __pcpu_local_irq_restore(___flags); \
___ret; \
})
@@ -165,9 +170,9 @@ do { \
#define this_cpu_generic_to_op(pcp, val, op) \
do { \
unsigned long __flags; \
- raw_local_irq_save(__flags); \
+ __pcpu_local_irq_save(__flags); \
raw_cpu_generic_to_op(pcp, val, op); \
- raw_local_irq_restore(__flags); \
+ __pcpu_local_irq_restore(__flags); \
} while (0)
@@ -175,9 +180,9 @@ do { \
({ \
TYPEOF_UNQUAL(pcp) __ret; \
unsigned long __flags; \
- raw_local_irq_save(__flags); \
+ __pcpu_local_irq_save(__flags); \
__ret = raw_cpu_generic_add_return(pcp, val); \
- raw_local_irq_restore(__flags); \
+ __pcpu_local_irq_restore(__flags); \
__ret; \
})
@@ -185,9 +190,9 @@ do { \
({ \
TYPEOF_UNQUAL(pcp) __ret; \
unsigned long __flags; \
- raw_local_irq_save(__flags); \
+ __pcpu_local_irq_save(__flags); \
__ret = raw_cpu_generic_xchg(pcp, nval); \
- raw_local_irq_restore(__flags); \
+ __pcpu_local_irq_restore(__flags); \
__ret; \
})
@@ -195,9 +200,9 @@ do { \
({ \
bool __ret; \
unsigned long __flags; \
- raw_local_irq_save(__flags); \
+ __pcpu_local_irq_save(__flags); \
__ret = raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval); \
- raw_local_irq_restore(__flags); \
+ __pcpu_local_irq_restore(__flags); \
__ret; \
})
@@ -205,9 +210,9 @@ do { \
({ \
TYPEOF_UNQUAL(pcp) __ret; \
unsigned long __flags; \
- raw_local_irq_save(__flags); \
+ __pcpu_local_irq_save(__flags); \
__ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
- raw_local_irq_restore(__flags); \
+ __pcpu_local_irq_restore(__flags); \
__ret; \
})
