Re: [PATCH 1/1] OvmfPkg: Reserve the Ovmf work area as RT_DATA

["Min Xu" <min.m.xu@intel.com>]

On August 23, 2022 3:38 PM, Gerd Hoffmann wrote:
>   Hi,
> 
> > Ah, I forget to reserve the work-area as RT_Data in below code:
> >       BuildMemoryAllocationHob (
> >         (EFI_PHYSICAL_ADDRESS)(UINTN)FixedPcdGet32
> (PcdOvmfWorkAreaBase),
> >         (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfWorkAreaSize),
> >         PlatformInfoHob->S3Supported ? EfiACPIMemoryNVS :
> EfiRuntimeServicesData  <-- ACPI_NVS is not accessible either in OS-Runtime.
> >         );
> >
> https://github.com/tianocore/edk2/blob/master/OvmfPkg/Library/Platform
> > InitLib/MemDetect.c#L1022-L1026
> 
> With that changed to use EfiRuntimeServicesData unconditionally the page
> fault is gone.
> 
> > Gerd, do you think we can reserve Ovmf WorkArea as RT_Data even when
> S3 is supported?
> 
> Hmm, not fully sure how the various memory types are handled when the
> VM is suspended.
> 
Tom suggested that the work area should not  be kept around. In stead a PCD should be used.
https://edk2.groups.io/g/devel/message/92617

But the dynamic PCD is not thread-safe and it cannot be accessed by APs. 

Now we have 2 solutions to fix this issue.
1. Reserve the Ovmf work area as RT_DATA.
2. Split the CcProbeLib into 2 instances. See https://edk2.groups.io/g/devel/message/91132

Gerd & Tom, what's your thought?

Thanks
Min