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Date: Wed, 17 Aug 2022 13:04:57 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: devel@edk2.groups.io
Cc: min.m.xu@intel.com
Subject: CcProbeLib not working for runtime calls
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  Hi,

https://bugzilla.redhat.com/show_bug.cgi?id=2114858

I think the call chain is:

-> linux does efi runtime call
  -> some debug message printed
    -> OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c
      -> MdePkg/Library/BaseIoLibIntrinsic (IoWriteFifo8)
        -> OvmfPkg/Library/CcProbeLib (CcProbe)
          -> page fault when trying to access WorkArea

Hmm.

We could probably reserve the workarea page and register it for a
runtime mapping etc.  I suspect that'll only crash the in simliar ways a
little later because the tdx/sev code is not prepared to work on runtime
calls.  I'm also not sure this is possible to make work at all given
that #vc/#ve faults are handled by the linux kernel not ovmf at this
point.

So have CcProbe just return CcGuestTypeNonEncrypted when called at
runtime, hoping that the linux kernel handles #vc / #ve faults properly
should they occur?

take care,
  Gerd