[edk2-devel] [PATCH v3 1/5] UefiCpuPkg/SmmBaseHob.h: Add SMM Base HOB Data
Gerd Hoffmann
kraxel at redhat.com
Fri Feb 3 07:54:37 UTC 2023
On Fri, Feb 03, 2023 at 03:14:42AM +0000, Ni, Ray wrote:
> Gerd,
> Can you please explain a bit more on the chunk idea?
> > > to introduce a generic and reusable concept of chunked HOBs, so you can
> > > add helper functions to HobLib for splitting and reassembling, with a
> > > struct along the lines of:
> > >
> > > typedef struct {
> > > // offset and size of this particular chunk
> > > UINT32 ChunkOffset;
> > > UINT32 ChunkSize;
> > >
> > > // number of chunks and size of all chunks combined.
> > > UINT32 ChunkCount;
> > > UINT32 TotalSize;
> > >
> > > // chunk data
> > > UINT8 Data[0];
> > > } EFI_HOB_CHUNK;
Reassembling would work like this:
// once
AssembledHob = malloc(HobChunk->TotalSize);
// for each chunk
memcpy(AssembledHob + HobChunk->ChunkOffset, HobChunk->Data, HobChunk->ChunkSize);
Possible shortcut:
if (HobChunk->ChunkSize == HobChunk->TotalSize)
// data is not splitted into multiple chunks
AssembledHob = HobChunk->Data
Advantage: you avoid the allocation in case the data fits into a single
HOB. Disadvantage: you need to track whenever AssembledHob is allocated
(and must eventually be freed) or not.
HobChunk->ChunkCount is not really needed but might be useful for sanity
checking.
take care,
Gerd
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