Re: [Xen-devel] [PATCH v3 07/11] hvm/hpet: Init comparator64 like comparator.

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 04/23/14 11:23, Jan Beulich wrote:
> > > > On 17.04.14 at 19:43, <dslutz@xxxxxxxxxxx> wrote:
> > The software-developers-hpet-spec-1-0a.pdf says that the comparator
> > starts as all 1's.  Also make the hidden register comparator64 the same.
> >
> > Since only the hidden register comparator64 is used by hpet_save, it
> > needs to start out with the right value.
> But the immediately preceding patch arranged for the field to get
> suitably updated, so is this change really doing anything but
> cosmetics?
The preceding patch only makes a difference when the hpet is enabled.  A 
disabled
hpet (like when a guest is starting), should start with the value the 
spec says.
Both hpet_save and the guest reading the comparator register use 
comparator64
to get the value.  So instead of just adding the line with comparator64, 
I could also
delete the setting of .cmp.  I picked the simpler one (just add the init).

So either way, not doing this change and for example using xen-hvmctx on 
a guest
that was started paused, you see all 0 not all 1.

   -Don Slutz

> Jan

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