Re: [Qemu-devel] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF

["Yao, Jiewen" <jiewen.yao@intel.com>]

in real world, we deprecate AB-seg usage because they are vulnerable to smm cache poison attack.
I assume cache poison is out of scope in the virtual world, or there is a way to prevent ABseg cache poison. 

thank you!
Yao, Jiewen


> 在 2019年8月19日，上午3:50，Paolo Bonzini <pbonzini@redhat.com> 写道：
> 
>> On 17/08/19 02:20, Yao, Jiewen wrote:
>> [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.
> 
> Paolo