Re: [patch 1/2] x86_64 page fault NMI-safe

H. Peter Anvin
2010-07-15T23:48:41Z

On 07/15/2010 04:44 PM, Linus Torvalds wrote:
> On Thu, Jul 15, 2010 at 4:41 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> No, the problem is that without IST it'll try to drop the NMI stack
>> frame itself *on the user stack*.
>
> Oh, because SS has already been cleared, but rsp still points to the
> user stack? Ok, that does seem insurmountable.
>

Well, SS doesn't matter for 64 bits, but yes, RSP still points to the
user stack.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.