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SubjectRe: [PATCH] [PATCH] x86: Don't clobber top of pt_regs in nested NMI
>>> On 02.11.12 at 14:53, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Fri, 2012-11-02 at 09:51 -0400, Steven Rostedt wrote:
>> On Thu, 2012-11-01 at 19:53 +0000, Jan Beulich wrote:
>>
>> > There doesn't appear to be anything special about these adjustments, so I
>> > don't see what help would be required here - it ought to be the normal use
>> > of CFI_ADJUST_CFA_OFFSET that needs adding.
>>
>> This change look fine to you?
>>
>> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
>> index 52edf92..7ba5342 100644
>> --- a/arch/x86/kernel/entry_64.S
>> +++ b/arch/x86/kernel/entry_64.S
>> @@ -1796,10 +1796,12 @@ repeat_nmi:
>>
>> /* Make another copy, this one may be modified by nested NMIs */
>> addq $(10*8), %rsp
>> + CFI_ADJUST_CFA_OFFSET -10*8
>> .rept 5
>> pushq_cfi -6*8(%rsp)
>> .endr
>> subq $(5*8), %rsp
>> + CFI_ADJUST_CFA_OFFSET 5*8
>>
>> CFI_DEF_CFA_OFFSET SS+8-RIP
>> end_repeat_nmi:
>>
>
> Is that second one even needed? Or will the CFI_DEF_CFA_OFFSET SS+8-RIP
> fix it?

Yes it will (as long as no intervening instructions get added; that's
to say that I'd recommend removing the blank line to make clear
that instruction and annotation belong together).

Jan



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