Le 25/02/2022 à 11:24, Mahesh Salgaonkar a écrit : > 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> > --- > arch/powerpc/include/asm/interrupt.h | 15 +++++++++++++++ > arch/powerpc/include/asm/percpu.h | 2 ++ > arch/powerpc/kernel/setup_64.c | 3 +++ > 3 files changed, 20 insertions(+)
In file included from /linux/arch/powerpc/kernel/irq.c:57:0: /linux/arch/powerpc/include/asm/interrupt.h: In function 'interrupt_nmi_enter_prepare': /linux/arch/powerpc/include/asm/interrupt.h:337:109: error: '__percpu_embed_first_chunk' undeclared (first use in this function) /linux/arch/powerpc/include/asm/interrupt.h:337:109: note: each undeclared identifier is reported only once for each function it appears in In file included from /linux/arch/powerpc/kernel/irq.c:57:0: /linux/arch/powerpc/include/asm/interrupt.h: In function 'interrupt_nmi_exit_prepare': /linux/arch/powerpc/include/asm/interrupt.h:353:109: error: '__percpu_embed_first_chunk' undeclared (first use in this function) In file included from /linux/arch/powerpc/kernel/irq.c:57:0: /linux/arch/powerpc/include/asm/interrupt.h:366:1: error: label at end of compound statement skip_nmi_exit: ^ /linux/scripts/Makefile.build:288: recipe for target 'arch/powerpc/kernel/irq.o' failed make[3]: *** [arch/powerpc/kernel/irq.o] Error 1
