Re: [edk2-devel] [PATCH V5 0/2] Re-design CcProbeLib

Re: [edk2-devel] [PATCH V5 0/2] Re-design CcProbeLib

[Yao, Jiewen]

Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>

Merged https://github.com/tianocore/edk2/pull/3290



> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Min Xu
> Sent: Tuesday, August 30, 2022 9:04 AM
> To: devel@edk2.groups.io
> Cc: Xu, Min M <min.m.xu@intel.com>; Gerd Hoffmann
> <kraxel@redhat.com>; Aktas, Erdem <erdemaktas@google.com>; James
> Bottomley <jejb@linux.ibm.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Tom Lendacky <thomas.lendacky@amd.com>; Yuan Yu
> <yuanyu@google.com>
> Subject: [edk2-devel] [PATCH V5 0/2] Re-design CcProbeLib
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3974
> 
> CcProbeLib once was designed to probe the Confidential Computing guest
> type by checking the PcdOvmfWorkArea. But this memory is allocated with
> either EfiACPIMemoryNVS or EfiBootServicesData. It cannot be accessed
> after ExitBootService. Please see the detailed analysis in BZ#3974.
> 
> To fix this issue, CcProbeLib is re-designed as 2 implementation:
>  - SecPeiCcProbeLib
>  - DxeCcProbeLib
> 
> In SecPeiCcProbeLib we check the CC guest type by reading the
> PcdOvmfWorkArea. Because it is used in SEC / PEI and we don't worry
> about
> the issues in BZ#3974.
> 
> In DxeCcProbeLib we cache the GuestType in Ovmf work area in a global
> variable. After that the Guest type is returned with the cached value.
> So that we don't need to worry about the access to Ovmf work area after
> ExitBootService.
> 
> The reason why we probe CC guest type in 2 different ways is the global
> variable. Global variable cannot be used in SEC/PEI and CcProbe is called
> very frequently.
> 
> Code: https://github.com/mxu9/edk2/tree/CcProbeLib.BZ3974.v4
> 
> v5 changes:
>  - Fix typos in commit message.
>  - No other changes in code.
> 
> v4 changes:
>  - Read Cc guest type in both DxeCcProbeLib's constructor and CcProbe. So
>    that we guarantee the Cc guest type is read early enough.
> 
> v3 changes:
>  - Re-design CcProbeLib to 2 implementation: SecPeiCcProbeLib and
>    DxeCcProbeLib. The difference between the 2 implementation is the
>    cache of the CcGuestType.
> 
> v2 changes:
>  - Reserve Ovmf work-area as RT_DATA. See
>    https://edk2.groups.io/g/devel/message/92599
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Yuan Yu <yuanyu@google.com>
> Acked: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Min Xu <min.m.xu@intel.com>
> 
> Min M Xu (2):
>   OvmfPkg: Add SecPeiCcProbeLib
>   OvmfPkg: Update CcProbeLib to DxeCcProbeLib
> 
>  OvmfPkg/IntelTdx/IntelTdxX64.dsc              |  3 +-
>  OvmfPkg/Library/CcProbeLib/DxeCcProbeLib.c    | 68
> +++++++++++++++++++
>  OvmfPkg/Library/CcProbeLib/DxeCcProbeLib.inf  | 26 +++++++
>  .../{CcProbeLib.c => SecPeiCcProbeLib.c}      |  0
>  .../{CcProbeLib.inf => SecPeiCcProbeLib.inf}  |  8 +--
>  OvmfPkg/OvmfPkgX64.dsc                        |  5 +-
>  6 files changed, 104 insertions(+), 6 deletions(-)
>  create mode 100644 OvmfPkg/Library/CcProbeLib/DxeCcProbeLib.c
>  create mode 100644 OvmfPkg/Library/CcProbeLib/DxeCcProbeLib.inf
>  rename OvmfPkg/Library/CcProbeLib/{CcProbeLib.c => SecPeiCcProbeLib.c}
> (100%)
>  rename OvmfPkg/Library/CcProbeLib/{CcProbeLib.inf =>
> SecPeiCcProbeLib.inf} (65%)
> 
> --
> 2.29.2.windows.2
> 
> 
> 
> 
>