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Date: Wed, 15 Dec 2021 09:18:42 +0100
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Min Xu <min.m.xu@intel.com>
Cc: devel@edk2.groups.io, Ard Biesheuvel <ardb+tianocore@kernel.org>,
	Jordan Justen <jordan.l.justen@intel.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Erdem Aktas <erdemaktas@google.com>,
	James Bottomley <jejb@linux.ibm.com>,
	Jiewen Yao <jiewen.yao@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH V4 17/31] OvmfPkg: Update Sec to support Tdx
Message-ID: <20211215081842.stsakfl3ub3thycu@sirius.home.kraxel.org>
References: <cover.1639399598.git.min.m.xu@intel.com>
 <1ecb7543dda024e55e9f7a0253b0af0c610407c4.1639399598.git.min.m.xu@intel.com>
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> +EFI_STATUS
> +EFIAPI
> +BspAcceptMemoryResourceRange (
> +  IN EFI_PHYSICAL_ADDRESS  PhysicalAddress,
> +  IN EFI_PHYSICAL_ADDRESS  PhysicalEnd
> +  )
> +{
> +  EFI_STATUS  Status;
> +  UINT32      AcceptPageSize;
> +  UINT64      StartAddress1;
> +  UINT64      StartAddress2;
> +  UINT64      StartAddress3;
> +  UINT64      TotalLength;
> +  UINT64      Length1;
> +  UINT64      Length2;
> +  UINT64      Length3;
> +  UINT64      Pages;
> +
> +  AcceptPageSize = FixedPcdGet32 (PcdTdxAcceptPageSize);
> +  TotalLength    = PhysicalEnd - PhysicalAddress;
> +  StartAddress1  = 0;
> +  StartAddress2  = 0;
> +  StartAddress3  = 0;
> +  Length1        = 0;
> +  Length2        = 0;
> +  Length3        = 0;
> +
> +  if (TotalLength == 0) {
> +    return EFI_SUCCESS;
> +  }
> +
> +  if ((AcceptPageSize == SIZE_4KB) || (TotalLength <= SIZE_2MB)) {
> +    //
> +    // if total length is less than 2M, then we accept pages in 4k
> +    //
> +    StartAddress1  = 0;
> +    Length1        = 0;
> +    StartAddress2  = PhysicalAddress;
> +    Length2        = PhysicalEnd - PhysicalAddress;
> +    StartAddress3  = 0;
> +    Length3        = 0;
> +    AcceptPageSize = SIZE_4KB;

You've zero-initialized everything above, no need to do that again.
You also can just use StartAddress1 + Length1 which uses 4k pages
anyway.

> +  } else if (AcceptPageSize == SIZE_2MB) {
> +    //
> +    // Total length is bigger than 2M and Page Accept size 2M is supported.
> +    //
> +    if ((PhysicalAddress & ALIGNED_2MB_MASK) == 0) {

The logic is rather messy.  It should become much simpler if you update
PhysicalAddress and TotalLength.  You can also use the alignment macros.

    if (ALIGN_VALUE(PhysicalAddress, SIZE_2MB) != PhysicalAddress) {
        StartAddress1 = PhysicalAddress;
        Length1 = ALIGN_VALUE(PhysicalAddress, SIZE_2MB) - PhysicalAddress;
        PhysicalAddress += Length1;
        TotalLength -= Length1;
    }
    if (TotalLength > SIZE_2MB) {
        StartAddress2 = PhysicalAddress;
        Length2 = TotalLength & ~(UINT64)ALIGNED_2MB_MASK
        PhysicalAddress += Length2;
        TotalLength -= Length2;
    }
    if (TotalLength) {
        StartAddress3 = PhysicalAddress;
        Length3 = TotalLength;
    }

take care,
  Gerd