[Jiewen] That is OK. Then we MUST add the third adversary. -- Adversary: Simple hardware attacker, who can use device to perform DMA attack in the virtual world. NOTE: The DMA attack in the real world is out of scope. That is be handled by IOMMU in the real world, such as VTd. -- Please do clarify if this is TRUE.
In the real world: #1: the SMM MUST be non-DMA capable region. #2: the MMIO MUST be non-DMA capable region. #3: the stolen memory MIGHT be DMA capable region or non-DMA capable region. It depends upon the silicon design. #4: the normal OS accessible memory - including ACPI reclaim, ACPI NVS, and reserved memory not included by #3 - MUST be DMA capable region. As such, IOMMU protection is NOT required for #1 and #2. IOMMU protection MIGHT be required for #3 and MUST be required for #4. I assume the virtual environment is designed in the same way. Please correct me if I am wrong.
Correct. The 0x30000...0x3ffff area is the only problematic one; Igor's idea (or a variant, for example optionally remapping 0xa0000..0xaffff SMRAM to 0x30000) is becoming more and more attractive.
