Possible [BUG] PeiCore: HOBs after cache-as-RAM teardown

["Benjamin Doron" <benjamin.doron00@gmail.com>]

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Hi all,
I'm working on root-causing an issue where I'm unable to retrieve any debug logs after cache-as-RAM teardown on my MinPlatform board port for GSoC 2021. I'm using KabylakeOpenBoardPkg/PeiSerialPortLibSpiFlash.

My best guess at the moment is that it's related to HOBs, which this SerialPortLib uses. If I reinitialise the library stack, it largely works, but a HOB/context structure entry "CurrentWriteOffset" also looks like it's zeroed.

Also, GetFeatureImplemented() in MinPlatformPkg/Test/TestPointCheckLib/PeiTestPointCheckLib.c asserts with "Status = Not Found". Internally, the test point architecture uses HOBs. I don't think this should happen, so, if not for this, I would think that perhaps a pointer in the serial port library needed to be updated.

I can see that the heap is copied over to permanent memory by the PEI core dispatcher ( https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c#L881 ). However, I can't see that the HOB list pointer is updated, so it looks like it ( https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Pei/Hob/Hob.c#L44 ) still has the value that's copied over from the old PEI core's data ( https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Pei/PeiMain/PeiMain.c#L348 ).

Does this look like a bug, or might there be something else that I'm missing?

Best regards,
Benjamin

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