Commit-ID: 5fa10196bdb5f190f595ebd048490ee52dddea0f Gitweb: http://git.kernel.org/tip/5fa10196bdb5f190f595ebd048490ee52dddea0f Author: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> AuthorDate: Fri, 7 Mar 2014 15:05:20 -0800 Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> CommitDate: Fri, 7 Mar 2014 15:08:14 -0800 x86: Ignore NMIs that come in during early boot Don Zickus reports: A customer generated an external NMI using their iLO to test kdump worked. Unfortunately, the machine hung. Disabling the nmi_watchdog made things work. I speculated the external NMI fired, caused the machine to panic (as expected) and the perf NMI from the watchdog came in and was latched. My guess was this somehow caused the hang. ---- It appears that the latched NMI stays latched until the early page table generation on 64 bits, which causes exceptions to happen which end in IRET, which re-enable NMI. Therefore, ignore NMIs that come in during early execution, until we have proper exception handling. Reported-and-tested-by: Don Zickus <dzickus@xxxxxxxxxx> Link: http://lkml.kernel.org/r/1394221143-29713-1-git-send-email-dzickus@xxxxxxxxxx Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # v3.5+, older with some backport effort --- arch/x86/kernel/head_32.S | 7 ++++++- arch/x86/kernel/head_64.S | 6 +++++- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 81ba276..d2a2159 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -544,6 +544,10 @@ ENDPROC(early_idt_handlers) /* This is global to keep gas from relaxing the jumps */ ENTRY(early_idt_handler) cld + + cmpl $X86_TRAP_NMI,(%esp) + je is_nmi # Ignore NMI + cmpl $2,%ss:early_recursion_flag je hlt_loop incl %ss:early_recursion_flag @@ -594,8 +598,9 @@ ex_entry: pop %edx pop %ecx pop %eax - addl $8,%esp /* drop vector number and error code */ decl %ss:early_recursion_flag +is_nmi: + addl $8,%esp /* drop vector number and error code */ iret ENDPROC(early_idt_handler) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index e1aabdb..33f36c7 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -343,6 +343,9 @@ early_idt_handlers: ENTRY(early_idt_handler) cld + cmpl $X86_TRAP_NMI,(%rsp) + je is_nmi # Ignore NMI + cmpl $2,early_recursion_flag(%rip) jz 1f incl early_recursion_flag(%rip) @@ -405,8 +408,9 @@ ENTRY(early_idt_handler) popq %rdx popq %rcx popq %rax - addq $16,%rsp # drop vector number and error code decl early_recursion_flag(%rip) +is_nmi: + addq $16,%rsp # drop vector number and error code INTERRUPT_RETURN ENDPROC(early_idt_handler) -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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