Re: [edk2-devel] [PATCH V2 28/28] OvmfPkg: Add LocalApicTimerDxe

["Min Xu" <min.m.xu@intel.com>]

On October 12, 2021 9:02 PM, Gerd Hoffmann wrote:
> On Tue, Oct 05, 2021 at 11:39:39AM +0800, Min Xu wrote:
> > RFC： https://bugzilla.tianocore.org/show_bug.cgi?id=3429
> >
> > TDX guest supports LocalApicTimer. But in current OvmfPkg the
> > supported timer is 8254TimerDxe. So
> > gUefiOvmfPkgTokenSpaceGuid.PcdTimerSelector
> > is introduced to select the running Timer. The Timer driver will check
> > the TimerSelector in its entry point. The default Timer is 8254.
> 
> Hmm.
> 
> We already have a local apic timer implementation (XenTimerDxe).  Works fine
> with kvm, microvm already uses that.  See commit 76602f45dcd9
> ("OvmfPkg/Microvm: use XenTimerDxe (lapic timer)").
> 
> So, first I'd suggest to just use that (maybe rename the thing to avoid confusion
> as it isn't really Xen specific).
Thanks for reminder. Let me first do some more investigation about the XenTimerDxe. It will be better to use an existing lapic timer than introducing a new one.
> 
> Next question is whenever there is a need for a runtime switch.  I doubt it is
> possible to create a virtual machine without lapic, so switching ovmf from 8254
> (aka pit) to lapic unconditionally should work fine.
> Quick smoke test (patch below) shows no obvious problems.
Let me do some more investigation.
> 

Thanks.
Min