Messages in this thread |  | | Date | Wed, 18 Mar 2015 15:18:13 -0700 | | Subject | Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related? | | From | Linus Torvalds <> |
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On Wed, Mar 18, 2015 at 2:55 PM, Andy Lutomirski <luto@amacapital.net> wrote: > > On Xen, it goes to xen_sysret64, which touches the same percpu > variables that we touch on entry. So I still like my percpu vmap > fault hypothesis, even though I don't understand what would trigger > it.
I don't dislike the theory per se, but not only don't I see how it could happen on regular execution on a laptop, but I also don't see why this fault behavior would be new to 4.0.
(And I do believe that we should make sure that CPU bringup ends up faulting in the percpu area, even if I don't really see why that would be the issue here)
Afaik, the system call entry code hasn't changed at all.
What *has* changed is the "paranoid" handling (double-fault has that magical "paranoid=2" thing, for example) and the return to user-space code.
Which is really why I don't believe in that syscall thing. Not because it isn't the obvious culprit, but simply because it hasn't *changed*.
Or is there something subtle I've missed?
Linus
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