Re: [PATCH v7 11/22] x86/virt/seamldr: Shut down the current TDX module

Edgecombe, Rick P
2026-04-11T01:35:40Z

On Tue, 2026-03-31 at 05:41 -0700, Chao Gao wrote:
> The first step of TDX module updates is shutting down the current TDX
> Module. This step also packs state information that needs to be
> preserved across updates as handoff data, which will be consumed by the
> updated module. The handoff data is stored internally in the SEAM range
> and is hidden from the kernel.
>
> To ensure a successful update, the new module must be able to consume
> the handoff data generated by the old module. Since handoff data layout
> may change between modules, the handoff data is versioned. Each module
> has a native handoff version and provides backward support for several
> older versions.
>
> The complete handoff versioning protocol is complex as it supports both
> module upgrades and downgrades. See details in Intel® Trust Domain
> Extensions (Intel® TDX) Module Base Architecture Specification, Chapter
> "Handoff Versioning".
>
> Ideally, the kernel needs to retrieve the handoff versions supported by
> the current module and the new module and select a version supported by
> both. But, since this implementation chooses to only support module
> upgrades, simply request the current module to generate handoff data
> using its highest supported version, expecting that the new module will
> likely support it.

I feel like somewhere it's missing what this patch does. It explains the
reasoning for the handoff version selection, but nothing about implement
"MODULE_UPDATE_SHUTDOWN" or anything like that.

>
> Note that only one CPU needs to call the TDX module's shutdown API.
>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
> Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
> Reviewed-by: Kai Huang <kai.huang@intel.com>
> Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
> ---
> v5:
> - Massage changelog [Kai]
> - Avoid "refers to the global copy while populating the tdx_sys_info
> passed as a pointer" [Rick/Yilun]
>
> v4:
> - skip the whole handoff metadata if runtime updates are not supported
> [Yilun]
> v3:
> - remove autogeneration stuff in the changelog
> v2:
> - add a comment about how handoff version is chosen.
> - remove the first !ret in get_tdx_sys_info_handoff() as we edited the
> auto-generated code anyway
> - remove !! when determining whether a CPU is the primary one
> - remove unnecessary if-break nesting in TDP_SHUTDOWN
> ---
> arch/x86/include/asm/tdx_global_metadata.h | 5 +++++
> arch/x86/virt/vmx/tdx/seamldr.c | 11 ++++++++++-
> arch/x86/virt/vmx/tdx/tdx.c | 15 +++++++++++++++
> arch/x86/virt/vmx/tdx/tdx.h | 3 +++
> arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 20 ++++++++++++++++++++
> 5 files changed, 53 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/tdx_global_metadata.h b/arch/x86/include/asm/tdx_global_metadata.h
> index 40689c8dc67e..8a9ebd895e70 100644
> --- a/arch/x86/include/asm/tdx_global_metadata.h
> +++ b/arch/x86/include/asm/tdx_global_metadata.h
> @@ -40,12 +40,17 @@ struct tdx_sys_info_td_conf {
> u64 cpuid_config_values[128][2];
> };
>
> +struct tdx_sys_info_handoff {
> + u16 module_hv;
> +};
> +
> struct tdx_sys_info {
> struct tdx_sys_info_version version;
> struct tdx_sys_info_features features;
> struct tdx_sys_info_tdmr tdmr;
> struct tdx_sys_info_td_ctrl td_ctrl;
> struct tdx_sys_info_td_conf td_conf;
> + struct tdx_sys_info_handoff handoff;
> };
>
> #endif
> diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
> index 5964bbc67944..a8bfa30ee55f 100644
> --- a/arch/x86/virt/vmx/tdx/seamldr.c
> +++ b/arch/x86/virt/vmx/tdx/seamldr.c
> @@ -15,6 +15,7 @@
> #include <asm/seamldr.h>
>
> #include "seamcall_internal.h"
> +#include "tdx.h"
>
> /* P-SEAMLDR SEAMCALL leaf function */
> #define P_SEAMLDR_INFO 0x8000000000000000
> @@ -207,6 +208,7 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
> */
> enum module_update_state {
> MODULE_UPDATE_START,
> + MODULE_UPDATE_SHUTDOWN,
> MODULE_UPDATE_DONE,
> };
>
> @@ -246,8 +248,12 @@ static void ack_state(void)
> static int do_seamldr_install_module(void *seamldr_params)
> {
> enum module_update_state newstate, curstate = MODULE_UPDATE_START;
> + int cpu = smp_processor_id();
> + bool primary;
> int ret = 0;
>
> + primary = cpumask_first(cpu_online_mask) == cpu;
> +
> do {
> /* Chill out and re-read update_data. */
> cpu_relax();
> @@ -256,7 +262,10 @@ static int do_seamldr_install_module(void *seamldr_params)
> if (newstate != curstate) {
> curstate = newstate;
> switch (curstate) {
> - /* TODO: add the update steps. */
> + case MODULE_UPDATE_SHUTDOWN:
> + if (primary)
> + ret = tdx_module_shutdown();
> + break;
> default:
> break;
> }
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 172f6d4133b5..f87fad429f4e 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -1176,6 +1176,21 @@ int tdx_enable(void)
> }
> EXPORT_SYMBOL_FOR_KVM(tdx_enable);
>
> +int tdx_module_shutdown(void)
> +{
> + struct tdx_module_args args = {};
> +
> + /*
> + * Shut down the TDX module and prepare handoff data for the next
> + * TDX module. This SEAMCALL requires a handoff version. Use the
> + * module's handoff version, as it is the highest version the
> + * module can produce and is more likely to be supported by new
> + * modules as new modules likely have higher handoff version.
> + */

This one could probably be made less verbose too.

> + args.rcx = tdx_sysinfo.handoff.module_hv;
> + return seamcall_prerr(TDH_SYS_SHUTDOWN, &args);
> +}
> +
> static bool is_pamt_page(unsigned long phys)
> {
> struct tdmr_info_list *tdmr_list = &tdx_tdmr_list;
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 82bb82be8567..1c4da9540ae0 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -46,6 +46,7 @@
> #define TDH_PHYMEM_PAGE_WBINVD 41
> #define TDH_VP_WR 43
> #define TDH_SYS_CONFIG 45
> +#define TDH_SYS_SHUTDOWN 52
>
> /*
> * SEAMCALL leaf:
> @@ -118,4 +119,6 @@ struct tdmr_info_list {
> int max_tdmrs; /* How many 'tdmr_info's are allocated */
> };
>
> +int tdx_module_shutdown(void);
> +
> #endif
> diff --git a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> index 34c050d74b56..225e157805e8 100644
> --- a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> +++ b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> @@ -100,6 +100,19 @@ static int get_tdx_sys_info_td_conf(struct tdx_sys_info_td_conf *sysinfo_td_conf
> return ret;
> }
>
> +static int get_tdx_sys_info_handoff(struct tdx_sys_info_handoff *sysinfo_handoff)
> +{
> + int ret;
> + u64 val;
> +
> + ret = read_sys_metadata_field(0x8900000100000000, &val);
> + if (ret)
> + return ret;
> +
> + sysinfo_handoff->module_hv = val;
> + return 0;
> +}
> +
> static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
> {
> int ret = 0;
> @@ -116,5 +129,12 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
> ret = ret ?: get_tdx_sys_info_td_ctrl(&sysinfo->td_ctrl);
> ret = ret ?: get_tdx_sys_info_td_conf(&sysinfo->td_conf);
>
> + /*
> + * Don't treat a module that doesn't support update as a failure.
> + * Only read the metadata optionally.
> + */
> + if (tdx_supports_runtime_update(sysinfo))
> + ret = ret ?: get_tdx_sys_info_handoff(&sysinfo->handoff);
> +
> return ret;
> }