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Date: Tue, 11 Jan 2022 10:29:41 +0100
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: sebastien.boeuf@intel.com
Cc: devel@edk2.groups.io, jiewen.yao@intel.com, jordan.l.justen@intel.com
Subject: Re: [PATCH v2 02/10] OvmfPkg/CloudHv: Replace legacy 8254 PIT with local APIC timer
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On Mon, Jan 10, 2022 at 06:47:22PM +0100, sebastien.boeuf@intel.com wrote:
> From: Sebastien Boeuf <sebastien.boeuf@intel.com>
> 
> Cloud Hypervisor doesn't emulate the legacy 8254 PIT, which is why
> instead of relying on it as the timer UEFI services, rely on the
> XenTimerDxe implementation. This is not Xen specific, as it simply uses
> the local APIC timer triggering interrupts on the vector 32.

I think you must set PcdFSBClock for this to work properly.

When using kvm (which cloudhv does as far I know) this is simple as the
frequency is fixed then, see microvm dsc file.  With xen this is dynamic
so the xen platform init has some code to figure the frequency and set
the pcd.

take care,
  Gerd