Updating README to add snp functionality

Signed-off-by: Diego Gonzalez Villalobos <[email protected]>

README.md

@@ -5,16 +5,37 @@
 
 # sev
 
-The `sev` crate provides an implementation of [AMD Secure Encrypted
-Virtualization (SEV)](https://developer.amd.com/sev/) APIs.
+The `sev` crate provides an implementation of the [AMD Secure Encrypted
+Virtualization (SEV)](https://developer.amd.com/sev/) APIs and the [SEV Secure Nested Paging
+Firmware (SNP)] (https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56860.pdf) ABIs. 
+
+### SEV APIs
 
 The Linux kernel exposes two technically distinct AMD SEV APIs:
 
 1. An API for managing the SEV platform itself
 2. An API for managing SEV-enabled KVM virtual machines
 
-This crate implements both of those APIs and offers them to client
-code through a flexible and type-safe high level interface.
+This crate implements both of those APIs and offers them to client.
+code through a flexible and type-safe high-level interface.
+
+### SNP ABIs
+
+The exposed ASP (AMD Secure Processor) firmware gets an enhancement with the SEV-SNP update.
+The new exposed ABI has the same two functionalities as the SEV API:
+
+1. An ABI for managing the SEV-SNP platform itself
+2. An ABI for managing SEV-SNP enabled KVM virtual machines
+
+These new ABIs work only for **SEV-SNP** enabled hosts and guests.
+
+This crate now implements both the APIs for SEV management as well as the ABIs for SEV-SNP management.
+
+### SEV and SEV-SNP enablement
+
+By default, both the SEV and SEV-SNP libraries are compiled.
+Since both generations have similar functions, the library is still split by folders according to function, and inside the modules we separate the functionalities into `sev.rs` and `snp.rs` files.
+You can select to only compile `sev` or `snp`.
 
 ### Platform Management