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x86: Ignore NMIs that come in during early boot

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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@redhat.com>
Link: http://lkml.kernel.org/r/1394221143-29713-1-git-send-email-dzickus@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org> # v3.5+, older with some backport effort
This commit is contained in:
H. Peter Anvin 2014-03-07 15:05:20 -08:00
parent d4078e2322
commit 5fa10196bd
2 changed files with 11 additions and 2 deletions
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7
arch/x86/kernel/head_32.S
View File

@ -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)

6
arch/x86/kernel/head_64.S
View File

@ -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)