* [PATCH v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.
@ 2024-02-05 5:36 Mahesh Salgaonkar
2024-02-12 8:06 ` Christophe Leroy
0 siblings, 1 reply; 3+ messages in thread
From: Mahesh Salgaonkar @ 2024-02-05 5:36 UTC (permalink / raw)
To: = linuxppc-dev; +Cc: = Aneesh Kumar K.V, = Ganesh Goudar, = Nicholas Piggin
nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
interrupt handler) if percpu allocation comes from vmalloc area.
Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
percpu allocation is from the embedded first chunk. However with
CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
allocation can come from the vmalloc area.
With kernel command line "percpu_alloc=page" we can force percpu allocation
to come from vmalloc area and can see kernel crash in machine_check_early:
[ 1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
[ 1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
[ 1.215719] --- interrupt: 200
[ 1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
[ 1.215722] [c000000fffd731b0] [0000000000000000] 0x0
[ 1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8
Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
first chunk is not embedded.
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
---
Changes in v2:
- Rebase to upstream master
- Use jump_labels, if CONFIG_JUMP_LABEL is enabled, to avoid redoing the
test at each interrupt entry.
- v1 is at https://lore.kernel.org/linuxppc-dev/164578465828.74956.6065296024817333750.stgit@jupiter/
---
arch/powerpc/include/asm/interrupt.h | 14 ++++++++++++++
arch/powerpc/include/asm/percpu.h | 11 +++++++++++
arch/powerpc/kernel/setup_64.c | 12 ++++++++++++
3 files changed, 37 insertions(+)
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index a4196ab1d0167..3b4e17c23d9a9 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -336,6 +336,16 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
if (IS_ENABLED(CONFIG_KASAN))
return;
+ /*
+ * Likewise, do not use it in real mode if percpu first chunk is not
+ * embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
+ * are chances where percpu allocation can come from vmalloc area.
+ */
+#ifdef CONFIG_PPC64
+ if (IS_ENABLED(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && !is_embed_first_chunk)
+ return;
+#endif
+
/* Otherwise, it should be safe to call it */
nmi_enter();
}
@@ -351,6 +361,10 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
// no nmi_exit for a pseries hash guest taking a real mode exception
} else if (IS_ENABLED(CONFIG_KASAN)) {
// no nmi_exit for KASAN in real mode
+#ifdef CONFIG_PPC64
+ } else if (IS_ENABLED(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && !is_embed_first_chunk) {
+ // no nmi_exit if percpu first chunk is not embedded
+#endif
} else {
nmi_exit();
}
diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
index 8e5b7d0b851c6..6b4dce4e78d5f 100644
--- a/arch/powerpc/include/asm/percpu.h
+++ b/arch/powerpc/include/asm/percpu.h
@@ -12,6 +12,17 @@
#define __my_cpu_offset local_paca->data_offset
+#ifdef CONFIG_JUMP_LABEL
+DECLARE_STATIC_KEY_FALSE(__percpu_embed_first_chunk);
+
+#define is_embed_first_chunk \
+ (static_key_enabled(&__percpu_embed_first_chunk.key))
+
+#else /* !CONFIG_JUMP_LABEL */
+extern bool __percpu_embed_first_chunk;
+#define is_embed_first_chunk __percpu_embed_first_chunk
+
+#endif /* CONFIG_JUMP_LABEL */
#endif /* CONFIG_SMP */
#endif /* __powerpc64__ */
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 2f19d5e944852..674b6e1bebe9a 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -834,6 +834,11 @@ static __init int pcpu_cpu_to_node(int cpu)
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);
+#ifdef CONFIG_JUMP_LABEL
+DEFINE_STATIC_KEY_FALSE(__percpu_embed_first_chunk);
+#else
+bool __percpu_embed_first_chunk;
+#endif
void __init setup_per_cpu_areas(void)
{
@@ -869,6 +874,13 @@ void __init setup_per_cpu_areas(void)
pr_warn("PERCPU: %s allocator failed (%d), "
"falling back to page size\n",
pcpu_fc_names[pcpu_chosen_fc], rc);
+ else {
+#ifdef CONFIG_JUMP_LABEL
+ static_key_enable(&__percpu_embed_first_chunk.key);
+#else
+ __percpu_embed_first_chunk = true;
+#endif
+ }
}
if (rc < 0)
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.
2024-02-05 5:36 [PATCH v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt Mahesh Salgaonkar
@ 2024-02-12 8:06 ` Christophe Leroy
2024-02-12 15:32 ` Mahesh J Salgaonkar
0 siblings, 1 reply; 3+ messages in thread
From: Christophe Leroy @ 2024-02-12 8:06 UTC (permalink / raw)
To: Mahesh Salgaonkar, = linuxppc-dev
Cc: = Aneesh Kumar K.V, = Ganesh Goudar, = Nicholas Piggin
Le 05/02/2024 à 06:36, Mahesh Salgaonkar a écrit :
> [Vous ne recevez pas souvent de courriers de mahesh@linux.ibm.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>
> nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
> crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
> interrupt handler) if percpu allocation comes from vmalloc area.
>
> Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
> wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
> percpu allocation is from the embedded first chunk. However with
> CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
> allocation can come from the vmalloc area.
>
> With kernel command line "percpu_alloc=page" we can force percpu allocation
> to come from vmalloc area and can see kernel crash in machine_check_early:
>
> [ 1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
> [ 1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
> [ 1.215719] --- interrupt: 200
> [ 1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
> [ 1.215722] [c000000fffd731b0] [0000000000000000] 0x0
> [ 1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8
>
> Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
> first chunk is not embedded.
>
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> ---
> Changes in v2:
> - Rebase to upstream master
> - Use jump_labels, if CONFIG_JUMP_LABEL is enabled, to avoid redoing the
> test at each interrupt entry.
> - v1 is at https://lore.kernel.org/linuxppc-dev/164578465828.74956.6065296024817333750.stgit@jupiter/
> ---
> arch/powerpc/include/asm/interrupt.h | 14 ++++++++++++++
> arch/powerpc/include/asm/percpu.h | 11 +++++++++++
> arch/powerpc/kernel/setup_64.c | 12 ++++++++++++
> 3 files changed, 37 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
> index a4196ab1d0167..3b4e17c23d9a9 100644
> --- a/arch/powerpc/include/asm/interrupt.h
> +++ b/arch/powerpc/include/asm/interrupt.h
> @@ -336,6 +336,16 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
> if (IS_ENABLED(CONFIG_KASAN))
> return;
>
> + /*
> + * Likewise, do not use it in real mode if percpu first chunk is not
> + * embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
> + * are chances where percpu allocation can come from vmalloc area.
> + */
> +#ifdef CONFIG_PPC64
Instead of adding this #ifdef in middle of code, could you define
is_embed_first_chunk as always 'true' when CONFIG_PPC64 is not defined ?
> + if (IS_ENABLED(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && !is_embed_first_chunk)
> + return;
> +#endif
> +
> /* Otherwise, it should be safe to call it */
> nmi_enter();
> }
> @@ -351,6 +361,10 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
> // no nmi_exit for a pseries hash guest taking a real mode exception
> } else if (IS_ENABLED(CONFIG_KASAN)) {
> // no nmi_exit for KASAN in real mode
> +#ifdef CONFIG_PPC64
Same
> + } else if (IS_ENABLED(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && !is_embed_first_chunk) {
> + // no nmi_exit if percpu first chunk is not embedded
> +#endif
> } else {
> nmi_exit();
> }
> diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
> index 8e5b7d0b851c6..6b4dce4e78d5f 100644
> --- a/arch/powerpc/include/asm/percpu.h
> +++ b/arch/powerpc/include/asm/percpu.h
> @@ -12,6 +12,17 @@
>
> #define __my_cpu_offset local_paca->data_offset
>
> +#ifdef CONFIG_JUMP_LABEL
> +DECLARE_STATIC_KEY_FALSE(__percpu_embed_first_chunk);
> +
> +#define is_embed_first_chunk \
> + (static_key_enabled(&__percpu_embed_first_chunk.key))
> +
> +#else /* !CONFIG_JUMP_LABEL */
> +extern bool __percpu_embed_first_chunk;
> +#define is_embed_first_chunk __percpu_embed_first_chunk
> +
> +#endif /* CONFIG_JUMP_LABEL */
> #endif /* CONFIG_SMP */
> #endif /* __powerpc64__ */
>
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 2f19d5e944852..674b6e1bebe9a 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -834,6 +834,11 @@ static __init int pcpu_cpu_to_node(int cpu)
>
> unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
> EXPORT_SYMBOL(__per_cpu_offset);
> +#ifdef CONFIG_JUMP_LABEL
Why this ifdef ? Even when CONFIG_JUMP_LABEL is not selected all this
should just work fine.
> +DEFINE_STATIC_KEY_FALSE(__percpu_embed_first_chunk);
> +#else
> +bool __percpu_embed_first_chunk;
> +#endif
>
> void __init setup_per_cpu_areas(void)
> {
> @@ -869,6 +874,13 @@ void __init setup_per_cpu_areas(void)
> pr_warn("PERCPU: %s allocator failed (%d), "
> "falling back to page size\n",
> pcpu_fc_names[pcpu_chosen_fc], rc);
> + else {
> +#ifdef CONFIG_JUMP_LABEL
> + static_key_enable(&__percpu_embed_first_chunk.key);
> +#else
> + __percpu_embed_first_chunk = true;
> +#endif
> + }
> }
>
> if (rc < 0)
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Re: [PATCH v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.
2024-02-12 8:06 ` Christophe Leroy
@ 2024-02-12 15:32 ` Mahesh J Salgaonkar
0 siblings, 0 replies; 3+ messages in thread
From: Mahesh J Salgaonkar @ 2024-02-12 15:32 UTC (permalink / raw)
To: Christophe Leroy
Cc: = linuxppc-dev, Ganesh Goudar, Nicholas Piggin, Aneesh Kumar K.V
On 2024-02-12 08:06:25 Mon, Christophe Leroy wrote:
>
>
> Le 05/02/2024 à 06:36, Mahesh Salgaonkar a écrit :
> > [Vous ne recevez pas souvent de courriers de mahesh@linux.ibm.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> >
> > nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
> > crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
> > interrupt handler) if percpu allocation comes from vmalloc area.
> >
> > Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
> > wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
> > percpu allocation is from the embedded first chunk. However with
> > CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
> > allocation can come from the vmalloc area.
> >
> > With kernel command line "percpu_alloc=page" we can force percpu allocation
> > to come from vmalloc area and can see kernel crash in machine_check_early:
> >
> > [ 1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
> > [ 1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
> > [ 1.215719] --- interrupt: 200
> > [ 1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
> > [ 1.215722] [c000000fffd731b0] [0000000000000000] 0x0
> > [ 1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8
> >
> > Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
> > first chunk is not embedded.
> >
> > Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> > ---
> > Changes in v2:
> > - Rebase to upstream master
> > - Use jump_labels, if CONFIG_JUMP_LABEL is enabled, to avoid redoing the
> > test at each interrupt entry.
> > - v1 is at https://lore.kernel.org/linuxppc-dev/164578465828.74956.6065296024817333750.stgit@jupiter/
> > ---
> > arch/powerpc/include/asm/interrupt.h | 14 ++++++++++++++
> > arch/powerpc/include/asm/percpu.h | 11 +++++++++++
> > arch/powerpc/kernel/setup_64.c | 12 ++++++++++++
> > 3 files changed, 37 insertions(+)
> >
> > diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
> > index a4196ab1d0167..3b4e17c23d9a9 100644
> > --- a/arch/powerpc/include/asm/interrupt.h
> > +++ b/arch/powerpc/include/asm/interrupt.h
> > @@ -336,6 +336,16 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
> > if (IS_ENABLED(CONFIG_KASAN))
> > return;
> >
> > + /*
> > + * Likewise, do not use it in real mode if percpu first chunk is not
> > + * embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
> > + * are chances where percpu allocation can come from vmalloc area.
> > + */
> > +#ifdef CONFIG_PPC64
>
> Instead of adding this #ifdef in middle of code, could you define
> is_embed_first_chunk as always 'true' when CONFIG_PPC64 is not defined ?
Will fix this in v3.
[...]
> > diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> > index 2f19d5e944852..674b6e1bebe9a 100644
> > --- a/arch/powerpc/kernel/setup_64.c
> > +++ b/arch/powerpc/kernel/setup_64.c
> > @@ -834,6 +834,11 @@ static __init int pcpu_cpu_to_node(int cpu)
> >
> > unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
> > EXPORT_SYMBOL(__per_cpu_offset);
> > +#ifdef CONFIG_JUMP_LABEL
>
> Why this ifdef ? Even when CONFIG_JUMP_LABEL is not selected all this
> should just work fine.
Yes you are right. I overlooked this. Will fix it in next revision.
Thanks for your review.
--
Mahesh J Salgaonkar
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-02-05 5:36 [PATCH v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt Mahesh Salgaonkar
2024-02-12 8:06 ` Christophe Leroy
2024-02-12 15:32 ` Mahesh J Salgaonkar
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