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SubjectRe: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel
Andi Kleen wrote:
>> This makes the whole thing unworthwhile. The vmload/vmsave pair costs
>> only 200 cycles (I should have started with this), and 120 cycles on the
>> heavyweight path plus complexity are not worth 200 cycles on the
>> lightweight path.
>>
>
> Actually to switch ISTs you need to change the TSS, not the IDT.
> But I suppose that won't be any faster.
>

I can't touch the TSS (that's the starting point of the exercise). The
plan was to have a copy of the IDT with all IST pointers zeroed out (or
to have per-cpu IDT and zero out the IST pointers when entering guest
mode, restoring them on context switch).

It's not worth it though.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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