Document TDX Module updates as a subsection of "TDX Host Kernel Support" to provide background information and cover key points that developers and users may need to know, for example: - update is done in stop_machine() context - update instructions and results - update policy and tooling Signed-off-by: Chao Gao --- Documentation/arch/x86/tdx.rst | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/Documentation/arch/x86/tdx.rst b/Documentation/arch/x86/tdx.rst index 61670e7df2f7..01ae560c7f66 100644 --- a/Documentation/arch/x86/tdx.rst +++ b/Documentation/arch/x86/tdx.rst @@ -99,6 +99,40 @@ initialize:: [..] virt/tdx: module initialization failed ... +TDX Module Runtime Updates +-------------------------- + +The TDX architecture includes a persistent SEAM loader (P-SEAMLDR) that +runs in SEAM mode separately from the TDX Module. The kernel can +communicate with P-SEAMLDR to perform runtime updates of the TDX Module. + +During updates, the TDX Module becomes unresponsive to other TDX +operations. To prevent components using TDX (such as KVM) from experiencing +unexpected errors during updates, updates are performed in stop_machine() +context. + +TDX Module updates have complex compatibility requirements; the new module +must be compatible with the current CPU, P-SEAMLDR, and running TDX Module. +Rather than implementing complex module selection and policy enforcement +logic in the kernel, userspace is responsible for auditing and selecting +appropriate updates. + +Updates use the standard firmware upload interface. See +Documentation/driver-api/firmware/fw_upload.rst for detailed instructions + +Successful updates are logged in dmesg: + [..] virt/tdx: version 1.5.20 -> 1.5.24 + +If updates failed, running TDs may be killed and further TDX operations may +be not possible until reboot. For detailed error information, see +Documentation/ABI/testing/sysfs-devices-faux-tdx-host. + +Given the risk of losing existing TDs, userspace should verify that the update +is compatible with the current system and properly validated before applying it. +A reference userspace tool that implements necessary checks is available at: + + https://github.com/intel/confidential-computing.tdx.tdx-module.binaries + TDX Interaction to Other Kernel Components ------------------------------------------ -- 2.47.3