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 mah...@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 <mah...@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