Thanks Min.
Merged - https://github.com/tianocore/edk2/pull/2790
> -----Original Message-----
> From: Xu, Min M <min.m.xu@intel.com>
> Sent: Tuesday, April 19, 2022 8:26 AM
> To: devel@edk2.groups.io
> Cc: Xu, Min M <min.m.xu@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Liu,
> Zhiguang <zhiguang.liu@intel.com>; James Bottomley <jejb@linux.ibm.com>;
> Yao, Jiewen <jiewen.yao@intel.com>; Gerd Hoffmann <kraxel@redhat.com>;
> Brijesh Singh <brijesh.singh@amd.com>; Aktas, Erdem
> <erdemaktas@google.com>; Tom Lendacky <thomas.lendacky@amd.com>
> Subject: [PATCH V4 0/7] Introduce CcProbe in MdePkg
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3902
>
> Bad IO performance in SEC phase is observed after TDX features was
> introduced. (after commit b6b2de884864 - "MdePkg: Support mmio for
> Tdx guest in BaseIoLibIntrinsic").
>
> This is because IsTdxGuest() will be called in each MMIO operation.
> It is trying to cache the result of the probe in the efi data segment.
> However, that doesn't work in SEC, because the data segment is read only
> (so the write seems to succeed but a read will always return the
> original value), leading to us calling TdIsEnabled() check for every
> mmio we do, which is causing the slowdown because it's very expensive.
>
> CcProbe is introduced in this patch-set. It is called in
> BaseIoLibIntrinsicSev instead of IsTdxGuest. There are 2 versions of
> the CcProbeLib. Null instance of CcProbe always returns
> CCGuestTypeNonEncrypted. Its OvmfPkg version checks the Ovmf work area
> and returns the CC guest type.
>
> In this patch-set another issue is fixed with CcProbe as well. If the
> working guest is SEV and in the beginning of SecMain.c TdIsEnabled()
> was called. At this point, exception handling is not established and
> a CPUID instruction will generate a #VC and cause the booting SEV guest
> to crash. Patch #7 is to fix this broken.
>
> Code is at: https://github.com/mxu9/edk2/tree/cc_probe.v4
>
> v4 changes:
> - Rename the field name in CC_GUEST_TYPE from CCXxx to CcXxx based
> on the community feedback.
>
> v3 changes:
> - Fix the broken issue in SEV guest at SecMain.c. Please refer to
> Patch #7.
>
> v2 changes:
> - Rename TdProbe to CcProbe to make the lib work for Confidential
> Computing guests.
> - Rename the GUEST_TYPE to CC_GUEST_TYPE and move it from
> WorkArea.h@OvmfPkg to ConfidentialComputingGuestAttr.h@MdePkg.
> This is because CcProbeLib is designed to return the CC Guest
> type and the lib is located at MdePkg.
> - Rename the CC_GUEST_TYPE's fields name to Camel style. See the
> commit message in patch #1.
>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Min Xu <min.m.xu@intel.com>
>
> Min Xu (7):
> MdePkg: Add CC_GUEST_TYPE in ConfidentialComputingGuestAttr.h
> OvmfPkg: Replace GUEST_TYPE with CC_GUEST_TYPE
> MdePkg: Add CcProbeLibNull
> OvmfPkg: Add CcProbeLib
> OvmfPkg: Add CcProbeLib in *.dsc
> MdePkg: Probe Cc guest in BaseIoLibIntrinsicSev
> OvmfPkg: Call CcProbe in SecMain.c instead of TsIsEnabled
>
> .../Include/ConfidentialComputingGuestAttr.h | 11 ++++++-
> MdePkg/Include/Library/CcProbeLib.h | 26 ++++++++++++++++
> .../BaseIoLibIntrinsicSev.inf | 1 +
> .../BaseIoLibIntrinsic/IoLibInternalTdx.c | 13 ++------
> .../Library/CcProbeLibNull/CcProbeLibNull.c | 26 ++++++++++++++++
> .../Library/CcProbeLibNull/CcProbeLibNull.inf | 21 +++++++++++++
> MdePkg/MdePkg.dec | 5 +++
> MdePkg/MdePkg.dsc | 1 +
> OvmfPkg/AmdSev/AmdSevX64.dsc | 1 +
> OvmfPkg/Bhyve/BhyveX64.dsc | 1 +
> OvmfPkg/CloudHv/CloudHvX64.dsc | 1 +
> OvmfPkg/Include/WorkArea.h | 9 +-----
> OvmfPkg/IntelTdx/IntelTdxX64.dsc | 1 +
> OvmfPkg/IntelTdx/Sec/SecMain.c | 6 ++--
> OvmfPkg/IntelTdx/Sec/SecMain.inf | 1 +
> .../PeiMemEncryptSevLibInternal.c | 2 +-
> .../SecMemEncryptSevLibInternal.c | 2 +-
> OvmfPkg/Library/CcProbeLib/CcProbeLib.c | 31 +++++++++++++++++++
> OvmfPkg/Library/CcProbeLib/CcProbeLib.inf | 25 +++++++++++++++
> OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c | 2 +-
> OvmfPkg/Microvm/MicrovmX64.dsc | 1 +
> OvmfPkg/OvmfPkgIa32.dsc | 1 +
> OvmfPkg/OvmfPkgIa32X64.dsc | 1 +
> OvmfPkg/OvmfPkgX64.dsc | 1 +
> OvmfPkg/OvmfXen.dsc | 1 +
> OvmfPkg/Sec/AmdSev.c | 2 +-
> OvmfPkg/Sec/SecMain.c | 5 +--
> OvmfPkg/Sec/SecMain.inf | 1 +
> 28 files changed, 170 insertions(+), 29 deletions(-)
> create mode 100644 MdePkg/Include/Library/CcProbeLib.h
> create mode 100644 MdePkg/Library/CcProbeLibNull/CcProbeLibNull.c
> create mode 100644 MdePkg/Library/CcProbeLibNull/CcProbeLibNull.inf
> create mode 100644 OvmfPkg/Library/CcProbeLib/CcProbeLib.c
> create mode 100644 OvmfPkg/Library/CcProbeLib/CcProbeLib.inf
>
> --
> 2.29.2.windows.2
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