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




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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