On Wed, Sep 01, 2021 at 04:29:03PM +0200, Markus Armbruster wrote:
> Michael Roth <michael.roth@xxxxxxx> writes:
>
> > From: Brijesh Singh <brijesh.singh@xxxxxxx>
> >
> > SEV-SNP support relies on a different set of properties/state than the
> > existing 'sev-guest' object. This patch introduces the 'sev-snp-guest'
> > object, which can be used to configure an SEV-SNP guest. For example,
> > a default-configured SEV-SNP guest with no additional information
> > passed in for use with attestation:
> >
> > -object sev-snp-guest,id=sev0
> >
> > or a fully-specified SEV-SNP guest where all spec-defined binary
> > blobs are passed in as base64-encoded strings:
> >
> > -object sev-snp-guest,id=sev0, \
> > policy=0x30000, \
> > init-flags=0, \
> > id-block=YWFhYWFhYWFhYWFhYWFhCg==, \
> > id-auth=CxHK/OKLkXGn/KpAC7Wl1FSiisWDbGTEKz..., \
> > auth-key-enabled=on, \
> > host-data=LNkCWBRC5CcdGXirbNUV1OrsR28s..., \
> > guest-visible-workarounds=AA==, \
> >
> > See the QAPI schema updates included in this patch for more usage
> > details.
> >
> > In some cases these blobs may be up to 4096 characters, but this is
> > generally well below the default limit for linux hosts where
> > command-line sizes are defined by the sysconf-configurable ARG_MAX
> > value, which defaults to 2097152 characters for Ubuntu hosts, for
> > example.
> >
> > Co-developed-by: Michael Roth <michael.roth@xxxxxxx>
> > Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> > Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> > ---
> > docs/amd-memory-encryption.txt | 77 ++++++++++-
> > qapi/qom.json | 60 ++++++++
> > target/i386/sev.c | 245 ++++++++++++++++++++++++++++++++-
> > 3 files changed, 379 insertions(+), 3 deletions(-)
> >
> > diff --git a/docs/amd-memory-encryption.txt b/docs/amd-memory-encryption.txt
> > index ffca382b5f..0d82e67fa1 100644
> > --- a/docs/amd-memory-encryption.txt
> > +++ b/docs/amd-memory-encryption.txt
> > @@ -22,8 +22,8 @@ support for notifying a guest's operating system when certain types of VMEXITs
> > are about to occur. This allows the guest to selectively share information with
> > the hypervisor to satisfy the requested function.
> >
> > -Launching
> > ----------
> > +Launching (SEV and SEV-ES)
> > +--------------------------
> > Boot images (such as bios) must be encrypted before a guest can be booted. The
> > MEMORY_ENCRYPT_OP ioctl provides commands to encrypt the images: LAUNCH_START,
> > LAUNCH_UPDATE_DATA, LAUNCH_MEASURE and LAUNCH_FINISH. These four commands
> > @@ -113,6 +113,79 @@ a SEV-ES guest:
> > - Requires in-kernel irqchip - the burden is placed on the hypervisor to
> > manage booting APs.
> >
> > +Launching (SEV-SNP)
> > +-------------------
> > +Boot images (such as bios) must be encrypted before a guest can be booted. The
> > +MEMORY_ENCRYPT_OP ioctl provides commands to encrypt the images:
> > +KVM_SNP_INIT, SNP_LAUNCH_START, SNP_LAUNCH_UPDATE, and SNP_LAUNCH_FINISH. These
> > +four commands together generate a fresh memory encryption key for the VM,
> > +encrypt the boot images for a successful launch.
> > +
> > +KVM_SNP_INIT is called first to initialize the SEV-SNP firmware and SNP
> > +features in the KVM. The feature flags value can be provided through the
> > +'init-flags' property of the 'sev-snp-guest' object.
> > +
> > ++------------+-------+----------+---------------------------------+
> > +| key | type | default | meaning |
> > ++------------+-------+----------+---------------------------------+
> > +| init_flags | hex | 0 | SNP feature flags |
> > ++-----------------------------------------------------------------+
> > +
> > +Note: currently the init_flags must be zero.
> > +
> > +SNP_LAUNCH_START is called first to create a cryptographic launch context
> > +within the firmware. To create this context, guest owner must provide a guest
> > +policy and other parameters as described in the SEV-SNP firmware
> > +specification. The launch parameters should be specified as described in the
> > +QAPI schema for the 'sev-snp-guest' object.
> > +
> > +The SNP_LAUNCH_START uses the following parameters (see the SEV-SNP
> > +specification for more details):
> > +
> > ++--------+-------+----------+----------------------------------------------+
> > +| key | type | default | meaning |
> > ++--------+-------+----------+----------------------------------------------+
> > +| policy | hex | 0x30000 | a 64-bit guest policy |
> > +| imi_en | bool | 0 | 1 when IMI is enabled |
> > +| ma_end | bool | 0 | 1 when migration agent is used |
> > +| gosvw | string| 0 | 16-byte base64 encoded string for the guest |
> > +| | | | OS visible workaround. |
> > ++--------+-------+----------+----------------------------------------------+
> > +
> > +SNP_LAUNCH_UPDATE encrypts the memory region using the cryptographic context
> > +created via the SNP_LAUNCH_START command. If required, this command can be called
> > +multiple times to encrypt different memory regions. The command also calculates
> > +the measurement of the memory contents as it encrypts.
> > +
> > +SNP_LAUNCH_FINISH finalizes the guest launch flow. Optionally, while finalizing
> > +the launch the firmware can perform checks on the launch digest computing
> > +through the SNP_LAUNCH_UPDATE. To perform the check the user must supply
> > +the id block, authentication blob and host data that should be included in the
> > +attestation report. See the SEV-SNP spec for further details.
> > +
> > +The SNP_LAUNCH_FINISH uses the following parameters, which can be configured
> > +by the corresponding parameters documented in the QAPI schema for the
> > +'sev-snp-guest' object.
> > +
> > ++------------+-------+----------+----------------------------------------------+
> > +| key | type | default | meaning |
> > ++------------+-------+----------+----------------------------------------------+
> > +| id_block | string| none | base64 encoded ID block |
> > ++------------+-------+----------+----------------------------------------------+
> > +| id_auth | string| none | base64 encoded authentication information |
> > ++------------+-------+----------+----------------------------------------------+
> > +| auth_key_en| bool | 0 | auth block contains author key |
> > ++------------+-------+----------+----------------------------------------------+
> > +| host_data | string| none | host provided data |
> > ++------------+-------+----------+----------------------------------------------+
> > +
> > +To launch a SEV-SNP guest (additional parameters are documented in the QAPI
> > +schema for the 'sev-snp-guest' object):
> > +
> > +# ${QEMU} \
> > + -machine ...,confidential-guest-support=sev0 \
> > + -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1
> > +
> > Debugging
> > -----------
> > Since the memory contents of a SEV guest are encrypted, hypervisor access to
> > diff --git a/qapi/qom.json b/qapi/qom.json
> > index 211e083727..ea39585026 100644
> > --- a/qapi/qom.json
> > +++ b/qapi/qom.json
> > @@ -775,6 +775,64 @@
> > '*policy': 'uint32',
> > '*handle': 'uint32' } }
> >
> > +##
> > +# @SevSnpGuestProperties:
> > +#
> > +# Properties for sev-snp-guest objects. Many of these are direct arguments
> > +# for the SEV-SNP KVM interfaces documented in the linux kernel source
> > +# documentation under 'amd-memory-encryption.rst'. Additional documentation
> > +# is also available in the QEMU source tree under
> > +# 'amd-memory-encryption.rst'.
> > +#
> > +# In addition to those files, please see the SEV-SNP Firmware Specification
> > +# (Rev 0.9) documentation for the SNP_INIT and
> > +# SNP_LAUNCH_{START,UPDATE,FINISH} firmware interfaces, which the KVM
> > +# interfaces are written against.
> > +#
> > +# @init-flags: as documented for the 'flags' parameter of the
> > +# KVM_SNP_INIT KVM command (default: 0)
> > +#
> > +# @policy: as documented for the 'policy' parameter of the
> > +# KVM_SNP_LAUNCH_START KVM command (default: 0x30000)
>
> These expose the host kernel's numerical encoding of over QMP. I'm not
> sure that's a good idea.
Most of these are the same as the actual arguments to firmware as defined by
the SNP spec, but I'll see if I can make the documentation here more
agnostic to the kernel interfaces and try to stick more to the SNP/firmware
spec.
>
> > +#
> > +# @guest-visible-workarounds: 16-byte, base64-encoded blob to report
> > +# hypervisor-defined workarounds, as documented
> > +# for the 'gosvm' parameter of the
> > +# KVM_SNP_LAUNCH_START KVM command.
> > +# (default: all-zero)
> > +#
> > +# @id-block: 8-byte, base64-encoded blob to provide the ID Block
> > +# structure documented in SEV-SNP spec, as documented for the
> > +# 'id_block_uaddr' parameter of the KVM_SNP_LAUNCH_FINISH
> > +# command (default: all-zero)
> > +#
> > +# @id-auth: 4096-byte, base64-encoded blob to provide the ID Authentication
> > +# Information Structure documented in SEV-SNP spec, as documented
> > +# for the 'id_auth_uaddr' parameter of the KVM_SNP_LAUNCH_FINISH
> > +# command (default: all-zero)
> > +#
> > +# @auth-key-enabled: true if 'id-auth' blob contains the Author Key
> > +# documented in the SEV-SNP spec, as documented for the
> > +# 'auth_key_en' parameter of the KVM_SNP_LAUNCH_FINISH
> > +# command (default: false)
> > +#
> > +# @host-data: 32-byte, base64-encoded user-defined blob to provide to the
> > +# guest, as documented for the 'host_data' parameter of the
> > +# KVM_SNP_LAUNCH_FINISH command (default: all-zero)
> > +#
> > +# Since: 6.2
> > +##
> > +{ 'struct': 'SevSnpGuestProperties',
> > + 'base': 'SevCommonProperties',
> > + 'data': {
> > + '*init-flags': 'uint64',
> > + '*policy': 'uint64',
> > + '*guest-visible-workarounds': 'str',
> > + '*id-block': 'str',
> > + '*id-auth': 'str',
> > + '*auth-key-enabled': 'bool',
> > + '*host-data': 'str' } }
> > +
> > ##
> > # @ObjectType:
> > #
> > @@ -816,6 +874,7 @@
> > 'secret',
> > 'secret_keyring',
> > 'sev-guest',
> > + 'sev-snp-guest',
> > 's390-pv-guest',
> > 'throttle-group',
> > 'tls-creds-anon',
> > @@ -873,6 +932,7 @@
> > 'secret': 'SecretProperties',
> > 'secret_keyring': 'SecretKeyringProperties',
> > 'sev-guest': 'SevGuestProperties',
> > + 'sev-snp-guest': 'SevSnpGuestProperties',
> > 'throttle-group': 'ThrottleGroupProperties',
> > 'tls-creds-anon': 'TlsCredsAnonProperties',
> > 'tls-creds-psk': 'TlsCredsPskProperties',
>
> Pretty much all Greek to me, but there are no obvious QAPI schema
> no-nos, so
>
> For the QAPI schema
> Acked-by: Markus Armbruster <armbru@xxxxxxxxxx>
>
> [...]
Thanks!
