Messages in this thread | | | Date | Thu, 24 Jul 2008 08:08:15 +0100 | From | "Jan Beulich" <> | Subject | Re: [PATCH] i386: improve double fault handling |
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>>> Joerg Roedel <joro@8bytes.org> 23.07.08 23:43 >>> >On Fri, Jul 18, 2008 at 01:30:42PM +0100, Jan Beulich wrote: >> Make the double fault handler use CPU-specific stacks. Add some >> abstraction to simplify future change of other exception handlers to go >> through task gates. > >What is the benefit of exception handlers going through task gates? >Hardware task switches are not very well supported in virtualization >(e.g. its has issues in KVM and is also not in Xen for a long time).
The main goal is to get to a different stack. While at present this is done only for the double fault, I think generally NMI and MCE should also do so, as they may be caused by a stack access (see x86-64, which runs them on IST stacks), and hence continuing to run on that same stack may not allow the exception to be handled.
Jan
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