Re: [edk2-devel] [PATCH] OvmfPkg: Set PcdCpuMaxLogicalProcessorNumber in OvmfXen

["Alejandro Vallejo via groups.io" <alejandro.vallejo=cloud.com@groups.io>]

Hi,

On 25/04/2024 08:31, Gerd Hoffmann wrote:
> On Wed, Apr 24, 2024 at 02:36:32PM +0100, Alejandro Vallejo wrote:
>> Bump the compile-time constant for maximum processor count from 64 to 128
>> in order to allow that many vCPUs to be brought online on Xen guests with
>> the default OVMF configuration.
> 
>> +  # UefiCpuPkg PCDs related to initial AP bringup and general AP management.
>> +  gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber|128
> 
> Note that this is a dynamic PCD, so you can set it at runtime to the
> number of vcpus present in the VM.  See MaxCpuCountInitialization() in
> OvmfPkg/PlatformPei/Platform.c for example.
> 
> take care,
>   Gerd
> 

Thanks for the heads up. Do you mean setting it at runtime through
fw_cfg? I saw PlatformMaxCpuCountInitialization() providing some
customizability, but Xen's toolstack doesn't provide fw_cfg at the
moment so it can't (as far as I've seen) use it.

I'm currently forced to do the override at compile time passing this...

    --pcd gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber=128

... to build.sh, but I'd rather have the default max match Xen's idea of
max unless there's a strong reason not to.

Cheers,
Alejandro


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