On Tue, 2024-11-05 at 01:24 -0500, Xiaoyao Li wrote: > diff --git a/docs/system/confidential-guest-support.rst > b/docs/system/confidential-guest-support.rst > index 0c490dbda2b7..66129fbab64c 100644 > --- a/docs/system/confidential-guest-support.rst > +++ b/docs/system/confidential-guest-support.rst > @@ -38,6 +38,7 @@ Supported mechanisms > Currently supported confidential guest mechanisms are: > > * AMD Secure Encrypted Virtualization (SEV) (see :doc:`i386/amd- > memory-encryption`) > +* Intel Trust Domain Extension (TDX) (see :doc:`i386/tdx`) > * POWER Protected Execution Facility (PEF) (see :ref:`power-papr- > protected-execution-facility-pef`) > * s390x Protected Virtualization (PV) (see :doc:`s390x/protvirt`) > > diff --git a/docs/system/i386/tdx.rst b/docs/system/i386/tdx.rst > new file mode 100644 > index 000000000000..60106b29bf72 > --- /dev/null > +++ b/docs/system/i386/tdx.rst > @@ -0,0 +1,155 @@ > +Intel Trusted Domain eXtension (TDX) > +==================================== > + > +Intel Trusted Domain eXtensions (TDX) refers to an Intel technology > that extends > +Virtual Machine Extensions (VMX) and Multi-Key Total Memory > Encryption (MKTME) > +with a new kind of virtual machine guest called a Trust Domain (TD). > A TD runs > +in a CPU mode that is designed to protect the confidentiality of its > memory > +contents and its CPU state from any other software, including the > hosting > +Virtual Machine Monitor (VMM), unless explicitly shared by the TD > itself. > + > +Prerequisites > +------------- > + > +To run TD, the physical machine needs to have TDX module loaded and > initialized > +while KVM hypervisor has TDX support and has TDX enabled. If those > requirements > +are met, the ``KVM_CAP_VM_TYPES`` will report the support of > ``KVM_X86_TDX_VM``. > + > +Trust Domain Virtual Firmware (TDVF) > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +Trust Domain Virtual Firmware (TDVF) is required to provide TD > services to boot > +TD Guest OS. TDVF needs to be copied to guest private memory and > measured before > +the TD boots. > + > +KVM vcpu ioctl ``KVM_TDX_INIT_MEM_REGION`` can be used to populates s/populates/populate > the TDVF > +content into its private memory. > + > +Since TDX doesn't support readonly memslot, TDVF cannot be mapped as > pflash > +device and it actually works as RAM. "-bios" option is chosen to > load TDVF. > + > +OVMF is the opensource firmware that implements the TDVF support. > Thus the > +command line to specify and load TDVF is ``-bios OVMF.fd`` > + > +Feature Configuration > +--------------------- > + > +Unlike non-TDX VM, the CPU features (enumerated by CPU or MSR) of a > TD is not s/is/are > +under full control of VMM. VMM can only configure part of features > of a TD on > +``KVM_TDX_INIT_VM`` command of VM scope ``MEMORY_ENCRYPT_OP`` ioctl. > + > +The configurable features have three types: > + > +- Attributes: > + - PKS (bit 30) controls whether Supervisor Protection Keys is > exposed to TD, > + which determines related CPUID bit and CR4 bit; > + - PERFMON (bit 63) controls whether PMU is exposed to TD. > + > +- XSAVE related features (XFAM): > + XFAM is a 64b mask, which has the same format as XCR0 or IA32_XSS > MSR. It > + determines the set of extended features available for use by the > guest TD. > + > +- CPUID features: > + Only some bits of some CPUID leaves are directly configurable by > VMM. > + > +What features can be configured is reported via TDX capabilities. > + > +TDX capabilities > +~~~~~~~~~~~~~~~~ > + > +The VM scope ``MEMORY_ENCRYPT_OP`` ioctl provides command > ``KVM_TDX_CAPABILITIES`` > +to get the TDX capabilities from KVM. It returns a data structure of > +``struct kvm_tdx_capabilities``, which tells the supported > configuration of > +attributes, XFAM and CPUIDs. > + > +TD attributes > +~~~~~~~~~~~~~ > + > +QEMU supports configuring raw 64-bit TD attributes directly via > "attributes" > +property of "tdx-guest" object. Note, it's users' responsibility to > provide a > +valid value because some bits may not supported by current QEMU or > KVM yet. > + > +QEMU also supports the configuration of individual attribute bits > that are > +supported by it, via propertyies of "tdx-guest" object. s/propertyies/properties > +E.g., "sept-ve-disable" (bit 63). > + > +MSR based features > +~~~~~~~~~~~~~~~~ > + > +Current KVM doesn't support MSR based feature (e.g., > MSR_IA32_ARCH_CAPABILITIES) > +configuration for TDX, and it's a future work to enable it in QEMU > when KVM adds > +support of it. > + > +Feature check > +~~~~~~~~~~~~~ > + > +QEMU checks if the final (CPU) features, determined by given cpu > model and > +explicit feature adjustment of "+featureA/-featureB", can be > supported or not. > +It can produce feature not supported warnning like > + > + "warning: host doesn't support requested feature: > CPUID.07H:EBX.intel-pt [bit 25]" > + > +It will also procude warning like s/procude/produce > + > + "warning: TDX forcibly sets the feature: > CPUID.80000007H:EDX.invtsc [bit 8]" > + > +if the fixed-1 feature is requested to be disabled explicitly. This > is newly > +added to QEMU for TDX because TDX has fixed-1 features that are > enfored enabled s/enfored/enforced > +by TDX module and VMM cannot disable them. > + > +Launching a TD (TDX VM) > +----------------------- > + > +To launch a TDX guest, below are new added and required: This sentence is missing a subject (such as "command line options"). > + > +.. parsed-literal:: > + > + |qemu_system_x86| \\ > + -object tdx-guest,id=tdx0 \\ > + -machine ...,kernel-irqchip=split,confidential-guest- > support=tdx0 \\ > + -bios OVMF.fd \\ > + > +restrictions > +------------ > + > + - kernel-irqchip must be split; > + > + - No readonly support for private memory; > + > + - No SMM support: SMM support requires manipulating the guset s/guset/guest > register states > + which is not allowed; > + > +Debugging > +--------- > + > +Bit 0 of TD attributes, is DEBUG bit, which decides if the TD runs > in off-TD > +debug mode. When in off-TD debug mode, TD's VCPU state and private > memory are > +accessible via given SEAMCALLs. This requires KVM to expose APIs to > invoke those > +SEAMCALLs and resonponding QEMU change. s/resonponding/corresponding
