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

[Tim Deegan <tim@xen.org>]

At 10:27 +0100 on 02 Jul (1372760862), Jan Beulich wrote:
> >>> On 02.07.13 at 11:11, Tim Deegan <tim@xen.org> wrote:
> > At 08:02 +0100 on 02 Jul (1372752161), Jan Beulich wrote:
> >> 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.
> >> 
> >> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> > 
> > Wasn't this going to have its own param, defaulting to off on create and
> > to on on migrate?  I suspect most people just leave the viridian flag on
> > for all domains.
> 
> In which case there would be no behavioral difference to what
> we're going to release with 4.3. (That's leaving aside the fact that
> I think people doing so is not the best practice.)

Why not?  The Viridian interfaces is pretty well essential for running
recent Windows, and shouldn't be harmful for other OSes.

Tim.

> In any case, while originally I indeed had considered having this
> have its own param, when putting the patch together I realized
> that there's little point (but extra work) in doing so.