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Re: [Xen-devel] Blocking upcall to dom0

To: Steven Hand <Steven.Hand@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Blocking upcall to dom0
From: Andrew Biggadike <biggadike@xxxxxxx>
Date: Tue, 1 Mar 2005 23:12:42 -0500
Cc: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
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Steven Hand <Steven.Hand@xxxxxxxxxxxx> wrote:
> > 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.
> Why not just use an event channel? This is precisely what they 
> are for. That way the invoking domain can simply kick an event, 
> and block waiting for a response. No new magic required in Xen
> at all.

That's what I was originally thinking, but from Keir's first reply it
seems that I can't arbitrarily block within Xen since stacks are per-CPU
rather than per-domain.

I'd like to block within Xen and resume at that same point in Xen, not
in the guest.  If I understand the flow of things correctly, then using
an event channel and blocking will resume the domain from the guest's
last execution context, rather than Xen's.  Please correct me if I'm


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