Re: [edk2-devel] [PATCH v8 04/10] OvmfPkg/CpuHotplugSmm: introduce UnplugCpus()

["Ankur Arora" <ankur.a.arora@oracle.com>]

On 2021-02-22 4:39 a.m., Laszlo Ersek wrote:
> On 02/22/21 08:19, Ankur Arora wrote:
>> Introduce UnplugCpus() which maps each APIC ID being unplugged
>> onto the hardware ID of the processor and informs PiSmmCpuDxeSmm
>> of removal by calling EFI_SMM_CPU_SERVICE_PROTOCOL.RemoveProcessor().
>>
>> With this change we handle the first phase of unplug where we collect
>> the CPUs that need to be unplugged and mark them for removal in SMM
>> data structures.
>>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Jordan Justen <jordan.l.justen@intel.com>
>> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>> Cc: Aaron Young <aaron.young@oracle.com>
>> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132
>> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
>> ---
>>
>> Notes:
>>      Addresses these review comments from v6:
>>       (1) Drop the empty line in the comment block around UnplugCpus().
>>       (2) Make the "did not find APIC ID" DEBUG_VERBOSE instead of DEBUG_INFO.
>>       (3) Un-Indented ("Outdented") the line following the comment "Ignore the
>>        unplug if APIC ID.
>>       (4) Remove the empty line between Status assignment and check.
>>       (5) Drop the "goto Fatal" logic and just return Status directly.
>>       (6) Handle both Plugging and Unplugging of CPUs in one go.
>>       (7) Also nest the EFI_STATUS check.
>>
>>   OvmfPkg/CpuHotplugSmm/CpuHotplug.c | 84 ++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 84 insertions(+)
>>
>> diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
>> index 3192bfea1f15..f07b5072749a 100644
>> --- a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
>> +++ b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
>> @@ -188,6 +188,83 @@ RevokeNewSlot:
>>   }
>>   
>>   /**
>> +  Process to be hot-unplugged CPUs, per QemuCpuhpCollectApicIds().
>> +
>> +  For each such CPU, report the CPU to PiSmmCpuDxeSmm via
>> +  EFI_SMM_CPU_SERVICE_PROTOCOL. If the to be hot-unplugged CPU is
>> +  unknown, skip it silently.
>> +
>> +  @param[in] ToUnplugApicIds    The APIC IDs of the CPUs that are about to be
>> +                                hot-unplugged.
>> +
>> +  @param[in] ToUnplugCount      The number of filled-in APIC IDs in
>> +                                ToUnplugApicIds.
>> +
>> +  @retval EFI_SUCCESS           Known APIC IDs have been removed from SMM data
>> +                                structures.
>> +
>> +  @return                       Error codes propagated from
>> +                                mMmCpuService->RemoveProcessor().
>> +**/
>> +STATIC
>> +EFI_STATUS
>> +UnplugCpus (
>> +  IN APIC_ID                      *ToUnplugApicIds,
>> +  IN UINT32                       ToUnplugCount
>> +  )
>> +{
>> +  EFI_STATUS Status;
>> +  UINT32     ToUnplugIdx;
>> +  UINTN      ProcessorNum;
>> +
>> +  ToUnplugIdx = 0;
>> +  while (ToUnplugIdx < ToUnplugCount) {
>> +    APIC_ID    RemoveApicId;
>> +
>> +    RemoveApicId = ToUnplugApicIds[ToUnplugIdx];
>> +
>> +    //
>> +    // mCpuHotPlugData->ApicId maps ProcessorNum -> ApicId. Use it to find
>> +    // the ProcessorNum for the APIC ID to be removed.
>> +    //
>> +    for (ProcessorNum = 0;
>> +         ProcessorNum < mCpuHotPlugData->ArrayLength;
>> +         ProcessorNum++) {
>> +      if (mCpuHotPlugData->ApicId[ProcessorNum] == RemoveApicId) {
>> +        break;
>> +      }
>> +    }
>> +
>> +    //
>> +    // Ignore the unplug if APIC ID not found
>> +    //
>> +    if (ProcessorNum == mCpuHotPlugData->ArrayLength) {
>> +      DEBUG ((DEBUG_VERBOSE, "%a: did not find APIC ID " FMT_APIC_ID
>> +        " to unplug\n", __FUNCTION__, RemoveApicId));
>> +      ToUnplugIdx++;
>> +      continue;
>> +    }
>> +
>> +    //
>> +    // Mark ProcessorNum for removal from SMM data structures
>> +    //
>> +    Status = mMmCpuService->RemoveProcessor (mMmCpuService, ProcessorNum);
>> +    if (EFI_ERROR (Status)) {
>> +      DEBUG ((DEBUG_ERROR, "%a: RemoveProcessor(" FMT_APIC_ID "): %r\n",
>> +        __FUNCTION__, RemoveApicId, Status));
>> +      return Status;
>> +    }
>> +
>> +    ToUnplugIdx++;
>> +  }
>> +
>> +  //
>> +  // We've removed this set of APIC IDs from SMM data structures.
>> +  //
>> +  return EFI_SUCCESS;
>> +}
>> +
>> +/**
>>     CPU Hotplug MMI handler function.
>>   
>>     This is a root MMI handler.
>> @@ -309,6 +386,13 @@ CpuHotplugMmi (
>>       }
>>     }
>>   
>> +  if (ToUnplugCount > 0) {
>> +    Status = UnplugCpus (mToUnplugApicIds, ToUnplugCount);
>> +    if (EFI_ERROR (Status)) {
>> +      goto Fatal;
>> +    }
>> +  }
>> +
>>     //
>>     // We've handled this MMI.
>>     //
>>
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks for the review!

Ankur