Re: [Xen-devel] Blocking upcall to dom0

[Andrew Biggadike <biggadike@xxxxxxx>]

Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
> In what context do you want to block? That of some other domain, or 
> block all domains while dom0 executes, or something else?

I want to block in the context of the unprivileged domain that was
running, and only block that domain.  In the hypercall example I gave,
I'd want the domain that invoked the hypercall to block within Xen until
dom0 completed the upcall.

> Xen doesn't support arbitrary blocking within itself since it only 
> maintains per-CPU stacks, not per-domain stacks.

Interesting.  So this means the scheduler is only ever invoked on
entry to and exit from Xen when there is no Xen state to worry about
saving?

> So you have to create a closure manually.

This is a bit more work than I had bargained for, but it seems doable.
Does temporarily setting a different schedule_tail() function to
restore the state from the closure seem reasonable?

Andrew


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