Re: [PATCH] i386: improve double fault handling

[Jan Beulich]

>>> Joerg Roedel <joro@xxxxxxxxxx> 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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