Re: [Xen-devel] [PATCH] hvm/hpet: Correctly gate the virtual HPET on HVM_PARAM_HPET_ENABLE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.15 at 15:40, <andrew.cooper3@xxxxxxxxxx> wrote:
> c/s 3f8e22de7 "x86 hvm: Allow HPET to be configured as a per-domain config
> option" introduced the parameter to conditionally enable the HPET.
> 
> However, having the check in hpet_range() does not have the intended effect.
> As currently implemented, when the HPET is disabled, the range is not 
> claimed
> and an ioreq is forwarded to qemu, which implements an HPET itself.
> 
> Properly disable the HPET by always claiming the range, dropping writes and
> reading ~0.

Hmm, while the patch certainly does what you describe above, is that
really correct? There could be something else at that address when
the HPET is disabled. Therefore I would rather think that qemu should
be told to also not make a HPET available when the option is off.

Jan


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