Re: [Xen-devel] [edk2-devel] [PATCH v4 35/35] OvmfPkg/OvmfXen: use RealTimeClockRuntimeDxe from EmbeddedPkg

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Aug 08, 2019 at 03:03:48PM +0100, Anthony PERARD wrote:
> On Wed, Aug 07, 2019 at 06:09:57PM +0200, Roger Pau Monné wrote:
> > On Mon, Jul 29, 2019 at 04:39:44PM +0100, Anthony PERARD wrote:
> > > A Xen PVH guest doesn't have a RTC that OVMF would expect, so
> > > PcatRealTimeClockRuntimeDxe fails to initialize and prevent the
> > > firmware from finish to boot. To prevent that, we will use
> > > XenRealTimeClockLib which simply always return the same time.
> > > This will work on both Xen PVH and HVM guests.
> > 
> > Not that this is not correct, but what's the point in requiring a
> > clock if it can be faked by always returning the same value?
> 
> It's not a clock that is required, it is a library that implements
> RealTimeClockLib. Something needs it, so it is provided, even if it is
> only to display the "current time".
> 
> > It seems like it's usage is not really required, and could indeed be
> > dropped altogether?
> 
> Way to much work to drop it. Also, I don't work to fork OVMF.
> 
> The ARM implementation of OVMF for Xen does the same thing and simply
> always return the same value.
> 
> > Alternatively, there's the PV clock which is available to PVH guests
> > and will return a proper time.
> 
> We might need to do that one day I guess, but right now it is just a
> nice to have.

Ack, thanks for the explanation.

Roger.

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