docs: security: Confidential computing intro and threat model for x86 virtualization

Kernel developers working on confidential computing for virtualized
environments in x86 operate under a set of assumptions regarding the Linux
kernel threat model that differs from the traditional view. Historically,
the Linux threat model acknowledges attackers residing in userspace, as
well as a limited set of external attackers that are able to interact with
the kernel through networking or limited HW-specific exposed interfaces
(e.g. USB, thunderbolt). The goal of this document is to explain additional
attack vectors that arise in the virtualized confidential computing space.
Reviewed-by: Larry Dewey <larry.dewey@amd.com>
Reviewed-by: David Kaplan <david.kaplan@amd.com>
Co-developed-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>

Message-ID: <98804f27-c2e7-74d6-d671-1eda927e19fe@amd.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/security/index.rst

@@ -6,6 +6,7 @@ Security Documentation
    :maxdepth: 1
 
    credentials
+   snp-tdx-threat-model
    IMA-templates
    keys/index
    lsm

MAINTAINERS

@@ -5196,6 +5196,12 @@ S:	Orphan
 W:	http://accessrunner.sourceforge.net/
 F:	drivers/usb/atm/cxacru.c
 
+CONFIDENTIAL COMPUTING THREAT MODEL FOR X86 VIRTUALIZATION (SNP/TDX)
+M:    Elena Reshetova <elena.reshetova@intel.com>
+M:    Carlos Bilbao <carlos.bilbao@amd.com>
+S:    Maintained
+F:    Documentation/security/snp-tdx-threat-model.rst
+
 CONFIGFS
 M:	Joel Becker <jlbec@evilplan.org>
 M:	Christoph Hellwig <hch@lst.de>