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SubjectRe: [PATCH 2/5] x86/entry/64, entry: Set up a valid sysenter stack and prepare for 32-bit merge
On Thu, Jul 23, 2015 at 9:01 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 23 Jul 2015 08:31:40 -0700
> Andy Lutomirski <luto@kernel.org> wrote:
>
>> Oddly, 64-bit kernels already allocate a percpu sysenter stack, but
>> they don't enable it. Enable the stack and tweak the rest of the
>> sysenter setup code to be similar to the 32-bit version.
>
> I'm curious. Did you do any investigation into the 64bit code to why it
> wasn't set? Do you know if that was just overlooked with some of the
> merging between i386 and x86_64 systems?
>
> I'm not asking you to do it if you have not, but if you have, I think
> it would be more comforting to know that it was just overlooked than
> there being some other subtle reason.

I think it's just that it was never necessary. #DB has always used
IST on x86_64 (IIRC it was like that in the very first commit), so the
sysenter stack was never actually referenced.


--Andy


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