target/i386: add Secure Encrypted Virtualization (SEV) object

Add a new memory encryption object 'sev-guest'. The object will be used
to create encrypted VMs on AMD EPYC CPU. The object provides the properties
to pass guest owner's public Diffie-hellman key, guest policy and session
information required to create the memory encryption context within the
SEV firmware.

e.g to launch SEV guest
 # $QEMU \
    -object sev-guest,id=sev0 \
    -machine ....,memory-encryption=sev0

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index 4c280142c5..6113bce08a 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4353,6 +4353,50 @@ contents of @code{iv.b64} to the second secret
          data=$SECRET,iv=$(<iv.b64)
 @end example
 
+@item -object sev-guest,id=@var{id},cbitpos=@var{cbitpos},reduced-phys-bits=@var{val},[sev-device=@var{string},policy=@var{policy},handle=@var{handle},dh-cert-file=@var{file},session-file=@var{file}]
+
+Create a Secure Encrypted Virtualization (SEV) guest object, which can be used
+to provide the guest memory encryption support on AMD processors.
+
+When memory encryption is enabled, one of the physical address bit (aka the
+C-bit) is utilized to mark if a memory page is protected. The @option{cbitpos}
+is used to provide the C-bit position. The C-bit position is Host family dependent
+hence user must provide this value. On EPYC, the value should be 47.
+
+When memory encryption is enabled, we loose certain bits in physical address space.
+The @option{reduced-phys-bits} is used to provide the number of bits we loose in
+physical address space. Similar to C-bit, the value is Host family dependent.
+On EPYC, the value should be 5.
+
+The @option{sev-device} provides the device file to use for communicating with
+the SEV firmware running inside AMD Secure Processor. The default device is
+'/dev/sev'. If hardware supports memory encryption then /dev/sev devices are
+created by CCP driver.
+
+The @option{policy} provides the guest policy to be enforced by the SEV firmware
+and restrict what configuration and operational commands can be performed on this
+guest by the hypervisor. The policy should be provided by the guest owner and is
+bound to the guest and cannot be changed throughout the lifetime of the guest.
+The default is 0.
+
+If guest @option{policy} allows sharing the key with another SEV guest then
+@option{handle} can be use to provide handle of the guest from which to share
+the key.
+
+The @option{dh-cert-file} and @option{session-file} provides the guest owner's
+Public Diffie-Hillman key defined in SEV spec. The PDH and session parameters
+are used for establishing a cryptographic session with the guest owner to
+negotiate keys used for attestation. The file must be encoded in base64.
+
+e.g to launch a SEV guest
+@example
+ # $QEMU \
+     ......
+     -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 \
+     -machine ...,memory-encryption=sev0
+     .....
+
+@end example
 @end table
 
 ETEXI