Documentation/virt/kvm/x86/intel-tdx.rst
.. SPDX-License-Identifier: GPL-2.0
Intel's Trust Domain Extensions (TDX) protect confidential guest VMs from the host and physical attacks. A CPU-attested software module called 'the TDX module' runs inside a new CPU isolated range to provide the functionalities to manage and run protected VMs, a.k.a, TDX guests or TDs.
Please refer to [1] for the whitepaper, specifications and other resources.
This documentation describes TDX-specific KVM ABIs. The TDX module needs to be initialized before it can be used by KVM to run any TDX guests. The host core-kernel provides the support of initializing the TDX module, which is described in the Documentation/arch/x86/tdx.rst.
:Type: vm ioctl, vcpu ioctl
For TDX operations, KVM_MEMORY_ENCRYPT_OP is re-purposed to be generic ioctl with TDX specific sub-ioctl() commands.
::
/* Trust Domain Extensions sub-ioctl() commands. */ enum kvm_tdx_cmd_id { KVM_TDX_CAPABILITIES = 0, KVM_TDX_INIT_VM, KVM_TDX_INIT_VCPU, KVM_TDX_INIT_MEM_REGION, KVM_TDX_FINALIZE_VM, KVM_TDX_GET_CPUID,
KVM_TDX_CMD_NR_MAX,
};
struct kvm_tdx_cmd { /* enum kvm_tdx_cmd_id / __u32 id; / flags for sub-command. If sub-command doesn't use this, set zero. / __u32 flags; / * data for each sub-command. An immediate or a pointer to the actual * data in process virtual address. If sub-command doesn't use it, * set zero. / __u64 data; / * Auxiliary error code. The sub-command may return TDX SEAMCALL * status code in addition to -Exxx. */ __u64 hw_error; };
:Type: vm ioctl :Returns: 0 on success, <0 on error
Return the TDX capabilities that current KVM supports with the specific TDX module loaded in the system. It reports what features/capabilities are allowed to be configured to the TDX guest.
::
struct kvm_tdx_capabilities { __u64 supported_attrs; __u64 supported_xfam;
/* TDG.VP.VMCALL hypercalls executed in kernel and forwarded to
* userspace, respectively
*/
__u64 kernel_tdvmcallinfo_1_r11;
__u64 user_tdvmcallinfo_1_r11;
/* TDG.VP.VMCALL instruction executions subfunctions executed in kernel
* and forwarded to userspace, respectively
*/
__u64 kernel_tdvmcallinfo_1_r12;
__u64 user_tdvmcallinfo_1_r12;
__u64 reserved[250];
/* Configurable CPUID bits for userspace */
struct kvm_cpuid2 cpuid;
};
:Type: vm ioctl :Returns: 0 on success, <0 on error
Perform TDX specific VM initialization. This needs to be called after KVM_CREATE_VM and before creating any VCPUs.
::
struct kvm_tdx_init_vm { __u64 attributes; __u64 xfam; __u64 mrconfigid[6]; /* sha384 digest / __u64 mrowner[6]; / sha384 digest / __u64 mrownerconfig[6]; / sha384 digest */
/* The total space for TD_PARAMS before the CPUIDs is 256 bytes */
__u64 reserved[12];
/*
* Call KVM_TDX_INIT_VM before vcpu creation, thus before
* KVM_SET_CPUID2.
* This configuration supersedes KVM_SET_CPUID2s for VCPUs because the
* TDX module directly virtualizes those CPUIDs without VMM. The user
* space VMM, e.g. qemu, should make KVM_SET_CPUID2 consistent with
* those values. If it doesn't, KVM may have wrong idea of vCPUIDs of
* the guest, and KVM may wrongly emulate CPUIDs or MSRs that the TDX
* module doesn't virtualize.
*/
struct kvm_cpuid2 cpuid;
};
:Type: vcpu ioctl :Returns: 0 on success, <0 on error
Perform TDX specific VCPU initialization.
:Type: vcpu ioctl :Returns: 0 on success, <0 on error
Initialize @nr_pages TDX guest private memory starting from @gpa with userspace provided data from @source_addr. @source_addr must be PAGE_SIZE-aligned.
Note, before calling this sub command, memory attribute of the range [gpa, gpa + nr_pages] needs to be private. Userspace can use KVM_SET_MEMORY_ATTRIBUTES to set the attribute.
If KVM_TDX_MEASURE_MEMORY_REGION flag is specified, it also extends measurement.
::
#define KVM_TDX_MEASURE_MEMORY_REGION (1UL << 0)
struct kvm_tdx_init_mem_region { __u64 source_addr; __u64 gpa; __u64 nr_pages; };
:Type: vm ioctl :Returns: 0 on success, <0 on error
Complete measurement of the initial TD contents and mark it ready to run.
:Type: vcpu ioctl :Returns: 0 on success, <0 on error
Get the CPUID values that the TDX module virtualizes for the TD guest. When it returns -E2BIG, the user space should allocate a larger buffer and retry. The minimum buffer size is updated in the nent field of the struct kvm_cpuid2.
::
struct kvm_cpuid2 { __u32 nent; __u32 padding; struct kvm_cpuid_entry2 entries[0]; };
struct kvm_cpuid_entry2 { __u32 function; __u32 index; __u32 flags; __u32 eax; __u32 ebx; __u32 ecx; __u32 edx; __u32 padding[3]; };
In addition to the standard KVM flow, new TDX ioctls need to be called. The control flow is as follows:
#. Check system wide capability
#. Create VM
#. Create VCPU
#. Initialize initial guest memory
#. Run VCPU
https://www.intel.com/content/www/us/en/developer/tools/trust-domain-extensions/documentation.html