Re: [RFC v1 0/3] Add VIRTIO_F_IOMMU_PLATFORM support

[Brijesh Singh <brijesh.singh@amd.com>]

On 7/28/17 7:52 PM, Brijesh Singh wrote:
[snip]
> AMD APM document a procedure which must be used to perform in-place
> encryption/decryption. We must follow those steps to ensure that data is
> flush into memory using the correct C-bit. Not doing so  may result in
> unpredictable results.
>
> http://support.amd.com/TechDocs/24593.pdf (Section 7.10.8)
I am wondering if UEFI provides APIs to  get two linear mapping of the
same physical address. The steps says we create two mapping of same
physical address with different C-bits. I will look into UEFI docs to
see if something like this exist otherwise we have to consider two
memcpy. Since its just for CommandBuffers (which usually are smaller
hence we may be okay from performance point of view. Also its just a
boot time thing, does not get used when guest OS is takes over. I will
investigate and see what works best without adding extra complexity in
the code :)

-Brijesh