Re: [Xen-devel] [PATCH] x86/HVM: tie RTC emulation mode to enabling of Viridian emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.07.13 at 10:01, Paul Durrant <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 02 July 2013 08:03
>> To: xen-devel
>> Cc: Paul Durrant; George Dunlap; Keir (Xen.org); Tim (Xen.org)
>> Subject: [PATCH] x86/HVM: tie RTC emulation mode to enabling of Viridian
>> emulation
>> 
>> As the mode not conforming to the hardware specification (by allowing
>> the guest to skip the REG C reads in its interrupt handler) is a
>> Viridian invention, it seems logical to tie this mode to that extension
>> being enabled. If the extension is disabled, proper hardware emulation
>> will be done instead.
>> 
>> The main thing necessary here is the synchronization of the RTC
>> emulation code and the setting of the respective flag in hvmloader's
>> creation of the ACPI WAET table.
>> 
> 
> Do we need to hardcode no_ack in the viridian case? Can we not be more 
> flexible and just have the WAET reflect whatever mode is in use?

We could, but is the extra work involved in coding this up (would
require a new HVM param) worth it? Newer Windows really wants
it that way...

Jan


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