[edk2-devel] [PATCH 0/3] MdePkg/MdeModulePkg: Introduce a pcd to control runtime services

[Laszlo Ersek]

Hello Zhichao,

On 07/17/19 09:37, Gao, Zhichao wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1907
> 
> UEFI spec 2.8 introduce a new variable L"RuntimeServicesSupported".
> If some runtime sevices is not supported at runtime phase, the variable
> should present at boot services. It is a bitmask value, the bit value of
> zero indicate the related runtime services is not supported at runtime
> phase.
> Add the difinition and use it to control Capsule runtime services.
> 
> Cc: Michael D Kinney <michael.d.kinney at intel.com>
> Cc: Liming Gao <liming.gao at intel.com>
> Cc: Jian J Wang <jian.j.wang at intel.com>
> Cc: Hao A Wu <hao.a.wu at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Star Zeng <star.zeng at intel.com>
> Cc: Sean Brogan <sean.brogan at microsoft.com>
> Cc: Michael Turner <Michael.Turner at microsoft.com>
> Cc: Bret Barkelew <Bret.Barkelew at microsoft.com>
> 
> Zhichao Gao (3):
>   MdePkg/UefiSpec.h: Add define of runtime services support
>   MdePkg: Indicate new pcd PcdRuntimeServicesSupport
>   MdeModulePkg/CapsuleRuntimeDxe: Control runtime services supported

Is a given platform expected to set the new PCD in accordance with other
platform settings?

Here's why I'm asking. OVMF does not support capsule services, as shown
by the following library class resolution in the OVMF DSC files:

  CapsuleLib|MdeModulePkg/Library/DxeCapsuleLibNull/DxeCapsuleLibNull.inf

OVMF will return EFI_UNSUPPORTED when the capsule runtime services are
invoked.

I'm not sure if the new PCD (and new UEFI variable,
"RuntimeServicesSupported") place new requirements on OVMF. It looks
like they do.

(1) If you agree, can you please include a new patch for OvmfPkg that
clears the EFI_RT_SUPPORTED_UPDATE_CAPSULE and
RT_SUPPORTED_QUERY_CAPSULE_CAPABILITIES bits in the PCD, in all three
DSC files?

(2) And, the same applies to all three ArmVirtPkg platforms:
ArmVirtQemu, ArmVirtQemuKernel, and ArmVirtXen.

(3) Furthermore, we already seem to have a related (generic) PCD, namely
PcdCapsuleInRamSupport. If that PCD is set to FALSE, then
UpdateCapsule() in
"MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleService.c" will return
EFI_UNSUPPORTED.

Should we introduce a consistency check somewhere, between the
capsule-related bits of the PcdRuntimeServicesSupport bitmask, and
PcdCapsuleInRamSupport?


I'm getting confused by the possible interactions between:
- PcdRuntimeServicesSupport
- PcdCapsuleInRamSupport
- and the CapsuleLib class resolution.

Thanks!
Laszlo

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