Re: [edk2-devel] [PATCH v3 08/13] OvmfPkg/PlatformInitLib: Create gEfiSmmSmramMemoryGuid

["Wu, Jiaxin" <jiaxin.wu@intel.com>]

> 
> > +    SmramHobDescriptorBlock                             =
> (EFI_SMRAM_HOB_DESCRIPTOR_BLOCK *)(Hob.Raw);
> 
> > +    SmramHobDescriptorBlock->Descriptor[0].PhysicalStart =
> PlatformInfoHob->LowMemory - TsegSize;
> > +    SmramHobDescriptorBlock->Descriptor[0].CpuStart      =
> PlatformInfoHob->LowMemory - TsegSize;
> > +    SmramHobDescriptorBlock->Descriptor[0].PhysicalSize  = EFI_PAGE_SIZE;
> > +    SmramHobDescriptorBlock->Descriptor[0].RegionState   =
> EFI_SMRAM_CLOSED | EFI_CACHEABLE | EFI_ALLOCATED;
> 
> > +    SmramHobDescriptorBlock->Descriptor[1].PhysicalStart =
> SmramHobDescriptorBlock->Descriptor[0].PhysicalStart + EFI_PAGE_SIZE;
> > +    SmramHobDescriptorBlock->Descriptor[1].CpuStart      =
> SmramHobDescriptorBlock->Descriptor[0].CpuStart + EFI_PAGE_SIZE;
> > +    SmramHobDescriptorBlock->Descriptor[1].PhysicalSize  = TsegSize -
> EFI_PAGE_SIZE;
> > +    SmramHobDescriptorBlock->Descriptor[1].RegionState   =
> EFI_SMRAM_CLOSED | EFI_CACHEABLE;
> 
> This is not going to fly.
> 
> First, smram allocation doesn't work that way.  Have a look at
> OvmfPkg/SmmAccess.  I guess that easily explains why this series
> breaks S3 suspend.
> 

Oh? Could you explain a bit more for 1) how smram allocation works? 2) what's the possible reason break the S3? I haven't check yet. 

> Second, storing these descriptors in a HOB (which is PEI memory)
> is questionable from a security point of view.
> 

HOB is only to expose the SMRAM address and size, not the contents in smram, what's the security concern?


Thanks,
Jiaxin


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