On Tue, 2016-01-26 at 16:22 +0000, Ian Jackson wrote:
> Ian Campbell writes ("Re: [PATCH 1/3] libxc/xc_domain_resume: Update
> comment."):
> > On Mon, 2016-01-25 at 16:06 -0500, Konrad Rzeszutek Wilk wrote:
> > > To hopefully clarify what it meant.
> ...
> > > + * 1. (fast=1) Resume with special return code (1) that the guest
> > > + * gets from SCHEDOP_shutdown:SHUTDOWN_suspend.
> >
> > "SCHEDOP_shutdown(SHUTDOWN_suspend)" looks more like the function call
> > which this in effect is.
> >
> > I think I'd say "Resume the guest without resetting the domain
> > environment.
> > The guests's call to SCHEDOP_shutdown(SHUTDOWN_suspend) will return 1".
> >
> > (assuming that is true re resetting)
>
> I'm not sure that `will return 1' is correct. IIRC there is some
> ... unpleasantness here, with something effectively corrupting the
> guest state in a way that the guest is supposed to expect and
> cooperate with.
The tools arrange for the hypercall to return 1, which the guest is indeed
expected to expect and cooperate, as with any PV interface call it makes.
They do this by intimate knowledge of the hypercall ABI (i.e. which
register is the return value) and one could certainly argue it ought to be
arranged in a less horrific way, but I think to characterise it as
"corrupting" is probably going to far.
>
> I haven't investigated the details recently. I do remember it being
> fiddly.
>
> Ian.
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