[edk2-devel] [PATCH 0/3] reuse the SevEsWork area

[Yao, Jiewen]

HI Brijesh
Thanks for the startup. Feedback below:

1) I don't think we need a PCD to indicate the header.
  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaHeaderSize|4|UINT32|0x51

Instead, if we define a HEADER structure, we can use sizeof() naturally. Otherwise, when we update this header, we need update 2 different places, which is not preferred.

typedef struct {
  UINT8                   GuestType;
  UINT8                   Reserved1[3];
} CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER;

2) I don't think we can define a common structure OVMF_WORK_AREA to contain SEV specific field.

typedef struct _OVMF_WORK_AREA {
  UINT8                   GuestType;
  UINT8                   Reserved1[3];

  SEC_SEV_ES_WORK_AREA    SevEsWorkArea;
} OVMF_WORK_AREA;

A common patter is to define each individual structure, then use UNION.

For example, 

typedef struct {
  UINT8                   GuestType;
  UINT8                   Reserved1[3];

  SEC_SEV_ES_WORK_AREA    SevEsWorkArea;
} SEV_WORK_AREA;

typedef union {
  CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER Header;
  SEV_WORK_AREA  Sev;
} OVMF_WORK_AREA;



> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Brijesh
> Singh via groups.io
> Sent: Thursday, August 5, 2021 4:20 AM
> To: devel at edk2.groups.io
> Cc: James Bottomley <jejb at linux.ibm.com>; Xu, Min M <min.m.xu at intel.com>;
> Yao, Jiewen <jiewen.yao at intel.com>; Tom Lendacky
> <thomas.lendacky at amd.com>; Justen, Jordan L <jordan.l.justen at intel.com>;
> Ard Biesheuvel <ardb+tianocore at kernel.org>; Erdem Aktas
> <erdemaktas at google.com>; Michael Roth <Michael.Roth at amd.com>; Brijesh
> Singh <brijesh.singh at amd.com>
> Subject: [edk2-devel] [PATCH 0/3] reuse the SevEsWork area
> 
> Based on the discussion on the mailing list, we agreed that instead
> of wasting extra page in the MEMFD, we can reuse the SevEsWorkArea
> buffer for the TDX. To avoid any confusion, lets introduce a OvmfWorkArea
> that will contains 32 bytes of header followed by the actual workarea.
> 
> While at it, move the code to clear the GHCB page from PageTable build
> to AmdSev.asm.
> 
> I have used the existing TDX BZ for it because the request came
> during the TDX patch review. if anyone have concern please let me know
> and I will happily create a new BZ.
> 
> Full tree is at: https://github.com/AMDESE/ovmf/tree/sev-new-work-area
> 
> Brijesh Singh (3):
>   OvmfPkg: introduce a common work area
>   OvmfPkg/ResetVector: update SEV support to use new work area format
>   OvmfPkg/ResetVector: move the GHCB page setup in AmdSev.asm
> 
> Cc: James Bottomley <jejb at linux.ibm.com>
> Cc: Min Xu <min.m.xu at intel.com>
> Cc: Jiewen Yao <jiewen.yao at intel.com>
> Cc: Tom Lendacky <thomas.lendacky at amd.com>
> Cc: Jordan Justen <jordan.l.justen at intel.com>
> Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
> Cc: Erdem Aktas <erdemaktas at google.com>
> 
>  OvmfPkg/OvmfPkg.dec                        |   6 ++
>  OvmfPkg/OvmfPkgX64.fdf                     |   9 +-
>  OvmfPkg/PlatformPei/PlatformPei.inf        |   4 +-
>  OvmfPkg/ResetVector/ResetVector.inf        |   1 +
>  OvmfPkg/Sec/SecMain.inf                    |   1 +
>  OvmfPkg/Include/Library/MemEncryptSevLib.h |  21 +---
>  OvmfPkg/Include/WorkArea.h                 |  53 ++++++++++
>  OvmfPkg/PlatformPei/MemDetect.c            |  32 +++---
>  OvmfPkg/Sec/SecMain.c                      |  25 ++++-
>  OvmfPkg/ResetVector/Ia32/AmdSev.asm        | 111 +++++++++++++++++----
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm  |  57 ++---------
>  OvmfPkg/ResetVector/ResetVector.nasmb      |   1 +
>  12 files changed, 213 insertions(+), 108 deletions(-)
>  create mode 100644 OvmfPkg/Include/WorkArea.h
> 
> --
> 2.17.1
> 
> 
> 
> 
> 



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