Re: [Xen-devel] PVH Whitelist Results / Windows Dom0

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.12.18 at 18:50, <roger.pau@xxxxxxxxxx> wrote:
> On Tue, Dec 04, 2018 at 05:46:38AM +0000, Connor Davis wrote:
>> >>> > > - 0x70
>> >>> > > - 0x71
>> 
>> These are accessed from reassert_nmi. This is only called from default_do_nmi
>> in the version the guest is based on (4.20-rc2).
> 
> Ops, forgot to answer this one.
> 
> Xen sets the 'CMOS RTC Not Present' flag in the IA-PC bootflags, those
> registers however are shared with the CMOS RAM.
> 
> I have to admit I'm not sure how this CMOS RTC flag is expected to
> behave, since the CMOS RTC / RAM implementation seems to be completely
> intertwined.

The first so many bytes in this space can be either RTC registers
or further bytes of CMOS RAM (to which various vendors have
created various other means of access mechanisms afaik). Hence
the flag set simply means there are no RTC registers there.
Whether CMOS RAM can be accessed through these ports is
unspecified by this flag being either set or clear, aiui (albeit I
think one might imply there is such RAM when the flag is set).

Jan



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