IGVM support has been implemented for Confidential Guests that support AMD SEV and AMD SEV-ES. Add some documentation that gives some background on the IGVM format and how to use it to configure a confidential guest.
Signed-off-by: Roy Hopkins <[email protected]> --- docs/system/i386/amd-memory-encryption.rst | 2 + docs/system/igvm.rst | 129 +++++++++++++++++++++ docs/system/index.rst | 1 + 3 files changed, 132 insertions(+) create mode 100644 docs/system/igvm.rst diff --git a/docs/system/i386/amd-memory-encryption.rst b/docs/system/i386/amd-memory-encryption.rst index e9bc142bc1..a253bf7db1 100644 --- a/docs/system/i386/amd-memory-encryption.rst +++ b/docs/system/i386/amd-memory-encryption.rst @@ -1,3 +1,5 @@ +.. _amd-sev: + AMD Secure Encrypted Virtualization (SEV) ========================================= diff --git a/docs/system/igvm.rst b/docs/system/igvm.rst new file mode 100644 index 0000000000..b07c11fa6e --- /dev/null +++ b/docs/system/igvm.rst @@ -0,0 +1,129 @@ +Independent Guest Virtual Machine (IGVM) support +================================================ + +IGVM files are designed to encapsulate all the information required to launch a +virtual machine on any given virtualization stack in a deterministic way. This +allows the cryptographic measurement of initial guest state for Confidential +Guests to be calculated when the IGVM file is built, allowing a relying party to +verify the initial state of a guest via a remote attestation. + +QEMU supports IGVM files through the Confidential Guest Support object. An igvm +filename can optionally be passed to the object which will subsequently be +parsed and used to configure the guest state prior to launching the guest. + +Further Information on IGVM +--------------------------- + +Information about the IGVM format, including links to the format specification +and documentation for the Rust and C libraries can be found at the project +repository: + +https://github.com/microsoft/igvm + + +Supported Platforms +------------------- + +Currently, IGVM files can be provided for Confidential Guests on host systems +that support AMD SEV and SEV-ES running under KVM. + + +Limitations when using IGVM with AMD SEV and SEV-ES +--------------------------------------------------- + +IGVM files configure the initial state of the guest using a set of directives. +Not every directive is supported by every Confidential Guest type. For example, +AMD SEV does not support encrypted save state regions, therefore setting the +initial CPU state using IGVM for SEV is not possible. When an IGVM file contains +directives that are not supported for the active platform, an error is displayed +and the guest launch is aborted. + +The table below describes the list of directives that are supported for SEV and +SEV-ES. + +.. list-table:: SEV & SEV-ES Supported Directives + :widths: 35 65 + :header-rows: 1 + + * - IGVM directive + - Notes + * - IGVM_VHT_PAGE_DATA + - ``NORMAL`` zero, measured and unmeasured page types are supported. Other + page types result in an error. + * - IGVM_VHT_PARAMETER_AREA + - + * - IGVM_VHT_PARAMETER_INSERT + - + * - IGVM_VHT_MEMORY_MAP + - The memory map page is populated using entries from the E820 table. + * - IGVM_VHT_VP_COUNT_PARAMETER + - The guest parameter page is populated with the CPU count. + * - IGVM_VHT_ENVIRONMENT_INFO_PARAMETER + - The ``memory_is_shared`` parameter is set to 1 in the guest parameter + page. + +.. list-table:: Additional SEV-ES Supported Directives + :widths: 25 75 + :header-rows: 1 + + * - IGVM directive + - Notes + * - IGVM_VHT_VP_CONTEXT + - Setting of the initial CPU state for the boot CPU and additional CPUs is + supported with limitations on the fields that can be provided in the + VMSA. See below for details on which fields are supported. + +Initial CPU state with SEV-ES VMSA +---------------------------------- + +The initial state of guest CPUs can be defined in the IGVM file for AMD SEV-ES. +The state data is provided as a VMSA structure as defined in Table B-4 in the +AMD64 Architecture Programmer's Manual, Volume 2 [1]. + +The IGVM VMSA is translated to CPU state in QEMU which is then synchronized +by KVM to the guest VMSA during the launch process where it contributes to the +launch measurement. See :ref:`amd-sev` for details on the launch process and +guest launch measurement. + +It is important that no information is lost or changed when translating the +VMSA provided by the IGVM file into the VSMA that is used to launch the guest. +Therefore, QEMU restricts the VMSA fields that can be provided in the IGVM +VMSA structure to the following registers: + +RAX, RCX, RDX, RBX, RBP, RSI, RDI, R8-R15, RSP, RIP, CS, DS, ES, FS, GS, SS, +CR0, CR3, CR4, XCR0, EFER. + +When processing the IGVM file, QEMU will check if any fields other than the +above are non-zero and generate an error if this is the case. + +Firmware Images with IGVM +------------------------- + +When an IGVM filename is specified for a Confidential Guest Support object it +overrides the default handling of system firmware: the firmware image, such as +an OVMF binary should be contained as a payload of the IGVM file and not +provided as a flash drive or via the ``-bios`` parameter. The default QEMU +firmware is not automatically populated into the guest memory space. + +If an IGVM file is provided along with either the ``-bios`` parameter or pflash +devices then an error is displayed and the guest startup is aborted. + +Running a Confidential Guest configured using IGVM +-------------------------------------------------- + +To run a confidential guest configured with IGVM you need to add the +``igvm-file`` parameter to the "confidential guest support" object: + +Example (for AMD SEV):: + + qemu-system-x86_64 \ + <other parameters> \ + -machine ...,confidential-guest-support=sev0 \ + -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1,igvm-file=/path/to/guest.igvm + +References +---------- + +[1] AMD64 Architecture Programmer's Manual, Volume 2: System Programming + Rev 3.41 + https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf \ No newline at end of file diff --git a/docs/system/index.rst b/docs/system/index.rst index c21065e519..6235dfab87 100644 --- a/docs/system/index.rst +++ b/docs/system/index.rst @@ -38,4 +38,5 @@ or Hypervisor.Framework. security multi-process confidential-guest-support + igvm vm-templating -- 2.43.0
