Re: [PATCH v9 2/3] trace,x86: add x86 irq vector tracepoints

["H. Peter Anvin" <hpa@zytor.com>]

On 02/18/2013 08:24 PM, Steven Rostedt wrote:
> On Mon, 2013-02-18 at 15:49 -0800, H. Peter Anvin wrote:
> 
>> What about the following:
>>
>>> The base address of the IDT doesn't generally change... the one
>>> exception is when we do the funny NMI workaround.
>>>
>>> For that reason, I would be happier if we just restored the standard
>>> value instead of saving/restoring stuff.
> 
> Basically what you are saying, is to have his code do what the NMI code
> originally did, but can't now, due to there being another IDT table
> (from Seiji's changes).
> 
> static void switch_to_trace_idt(void *arg)
> {
>      load_idt(&trace_idt_descr);
> }
> 
> static void restore_original_idt(void *arg)
> {
>      load_idt(this_cpu_ptr(&idt_descr));
> }
> 

Yes.  If there needs to be handshaking about whose IDT is currently
installed I'm much happier if that handshake is done explicitly, rather
than as a save/restore function which will break when we have to add
another one which for whatever reason isn't nesting.

	-hpa