Re: [PATCH 18/25] [PATCH] turn priviled operations into macros in entry.S

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On Wed, 8 Aug 2007, Andi Kleen wrote:

quoted

When I said "this part of the code I don't fully understand" I was not
talking about entry.S.  I understand entry.S very well, but the comment
was originally on the paranoid_restore code. Which I thought had to deal
with NMIs and such that I didn't worry about that I simply did the
default.

The paranoid path is used for more than just NMIs; it's also used for MCEs,
stack faults, double faults or debug exceptions. Anything that might
happen with a invalid stack or unknown GS state or system in other unknown
state.

If you can guarantee your hypervisor never injects any of those it could be ignored;
but at least losing debug exceptions would be probably not nice.

For now it does ignore them. But that's something to work on
for later versions of lguest64.  I want lguest out in the public and
working for the general case. I don't plan on ignoring the paranoid
section forever. But it's more on an anomaly for now. But you are right, I
want the debug stuff working. But I also need to walk before I can run ;-)

quoted

quoted

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 paranoid_restore\trace:
      RESTORE_ALL 8
-     iretq
+     INTERRUPT_RETURN

I suspect Xen will need much more changes anyways because of its
ring 3 guest. Are these changes sufficient for lguest?

This was really a general comment not especially applying to the
paranoid path.

Ah, OK, I assumed you were talking about just the previous code. But
rereading your post, I see it was more general.  Sorry, for the
miscommunication.

-- Steve