Re: [edk2-devel] [PATCH 12/16] OvmfPkg/PlatformPei: Retrieve APIC IDs from the hypervisor

["Lendacky, Thomas via groups.io" <thomas.lendacky=amd.com@groups.io>]

On 1/29/24 09:00, Gerd Hoffmann wrote:
> On Fri, Jan 26, 2024 at 04:13:11PM -0600, Tom Lendacky wrote:
>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654
>>
>> If the hypervisor supports retrieval of the vCPU APIC IDs, retrieve
>> them before any APs are actually started. The APIC IDs can be used
>> to start the APs for any SEV-SNP guest, but is a requirement for an
>> SEV-SNP guest that is running under an SVSM.
> 
>> +  ApicIds = AllocateReservedPages ((UINTN)PageCount);
> 
>> +  VmgExitStatus = CcExitVmgExit (Ghcb, SVM_EXIT_GET_APIC_IDS, (UINTN)ApicIds, 0);
> 
> Ah, you pass a pointer to GHCB_APIC_IDS instead of storing the data
> directly in the GHCB.  Scratch the patch #10 comment then.
> 
>> +  // Retrieve the APIC IDs if the hypervisor supports it. These will be used
>> +  // to always start APs using SNP AP Create.
>> +  //
>> +  if ((HvFeatures & GHCB_HV_FEATURES_APIC_ID_LIST) == GHCB_HV_FEATURES_APIC_ID_LIST) {
>> +    AmdSevSnpGetApicIds ();
>> +  }
> 
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> 
> This looks like it does not depend on the SVSM being present,
> is this correct?

Correct, this doesn't require the SVSM to be used. But when running under 
an SVSM, the SVSM requires this.

I could move this to the start of the series if you think that makes more 
sense.

Thanks,
Tom

> 
> take care,
>    Gerd
> 


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