Andi Kleen wrote:
> Ah I assumed the hypervisor would just check IF in ring 1 too.
> It would certainly make this easier, but then the additional trap
> of setting it would be also somewhat expensive agreed.
>
Xen doesn't do that because, while it could track sti/cli (expensively),
iret and pop
On Monday 04 June 2007 23:28, Jeremy Fitzhardinge wrote:
> The cli/sti instructions don't control the event mask, so they're
> effectively expensive no-ops (they trap into the hypervisor, are
> emulated as no-ops). But if you mean cli as a general term for
> "events/interrupts masked", then they c
Andi Kleen wrote:
> If you stay cli you don't need that. Why is it that it has to enable
> interrupts?
>
Bear in mind we're talking about running paravirt under Xen in ring 1.
The cli/sti instructions don't control the event mask, so they're
effectively expensive no-ops (they trap into the hy
On Monday 04 June 2007 22:33, Jeremy Fitzhardinge wrote:
> Hm, yes, I guess so. I'd assumed that softirq was in the WORK_NEEDED
> path of entry.S without checking; but anything which can set one of the
> WORK_NEEDED flags is an issue.
For interrupts it can be only signals or rescheduling.
> >>
Andi Kleen wrote:
> Not sure what a recursive exception is. You mean the interrupt?
>
Yeah, though Xen calls them events, so I chose a completely different
third term.
> It looks ...very... ug^w^wcomplicated.
>
I suppose, but you should look at the xen-unstable code by comparison...
But e
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