Re: [edk2-devel] [PATCH v2] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg block regression

["Michael Brown" <mcb30@ipxe.org>]

On 12/01/2023 13:22, Laszlo Ersek wrote:
>>> Detect the issue in PlatformMaxCpuCountInitialization(), and
>>> print an error message and *hang* if the issue is present.
>> 
>> Would this mean that OVMF would refuse to start with all current
>> distro versions of qemu (when not using KVM), or am I
>> misunderstanding?
> 
> Your understanding is correct.

I apologise in advance if this is a stupid question, but: given that we
can detect the issue (as per this patch), and given also:

>> On 12/01/2023 08:28, Laszlo Ersek wrote:
>>> In QEMU v5.1.0, the CPU hotplug register block misbehaves: the 
>>> negotiation protocol is (effectively) broken such that it
>>> suggests that switching from the legacy interface to the modern
>>> interface works, but in reality the switch never happens.
...would it work to detect the issue and treat it as "modern interface 
is not supported: continue to use the legacy interface"?  IOW, to treat 
"Present=0" as indicating that the modern interface is not supported.

Thanks,

Michael