[tip: x86/tdx] x86/virt/tdx: Restore TDX module state

["tip-bot2 for Chao Gao" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/tdx branch of tip:

Commit-ID:     069be08012cf372d5239817adb5a7a044730e9bd
Gitweb:        https://git.kernel.org/tip/069be08012cf372d5239817adb5a7a044730e9bd
Author:        Chao Gao <chao.gao@intel.com>
AuthorDate:    Wed, 20 May 2026 15:29:10 -07:00
Committer:     Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Tue, 26 May 2026 08:41:51 -07:00

x86/virt/tdx: Restore TDX module state

After per-CPU initialization, the module is nearly functional. It is
in a similar state to TDX initialization before TDH.SYS.CONFIG.

At this point, the kernel _could_ just repeat the boot-time sequence,
but that would land the new module in a slightly different state than
the old module.  This would leave old TDs unrunnable, which is not a
good outcome.

Thankfully, the "handoff" data saved during module shutdown should
contain all the information needed to restore the TDX module state to
exactly what it was before the update.

Restore TDX module state. The TDX module only needs a single copy so
only do this on the lead CPU.

Restoration errors can theoretically be handled in a few ways. For
instance, userspace could try to load a different TDX module version.
Or, the kernel could give up on the handoff process and just
reinitialize the new module from scratch, which would lose all
existing TDs.

Simply propagate errors to userspace. Ignore the idea of a
TD-destroying reinitialization. It would destroy data like a reboot
and if things have gone that wrong a reboot is probably the best
option anyway.

Note: the location and the format of handoff data is defined by the
TDX module. The new module knows where to get handoff data and how to
parse it. The kernel does not touch it at all.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://patch.msgid.link/20260520133909.409394-21-chao.gao@intel.com
Link: https://patch.msgid.link/20260520222910.7727219F@davehans-spike.ostc.intel.com
---
 arch/x86/virt/vmx/tdx/seamldr.c |  5 +++++
 arch/x86/virt/vmx/tdx/tdx.c     | 13 +++++++++++++
 arch/x86/virt/vmx/tdx/tdx.h     |  2 ++
 3 files changed, 20 insertions(+)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 5fdb36b..f5591d7 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -210,6 +210,7 @@ enum module_update_state {
 	MODULE_UPDATE_SHUTDOWN,
 	MODULE_UPDATE_CPU_INSTALL,
 	MODULE_UPDATE_CPU_INIT,
+	MODULE_UPDATE_RUN_UPDATE,
 	MODULE_UPDATE_DONE,
 };
 
@@ -291,6 +292,10 @@ static int do_seamldr_install_module(void *seamldr_params)
 		case MODULE_UPDATE_CPU_INIT:
 			ret = tdx_cpu_enable();
 			break;
+		case MODULE_UPDATE_RUN_UPDATE:
+			if (is_lead_cpu)
+				ret = tdx_module_run_update();
+			break;
 		default:
 			break;
 		}
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 080a2bc..d54c2ec 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1312,6 +1312,19 @@ int tdx_module_shutdown(void)
 	return 0;
 }
 
+int tdx_module_run_update(void)
+{
+	struct tdx_module_args args = {};
+	int ret;
+
+	ret = seamcall_prerr(TDH_SYS_UPDATE, &args);
+	if (ret)
+		return ret;
+
+	tdx_module_state.initialized = true;
+	return 0;
+}
+
 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 f0c20de..bdfd0e1 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -47,6 +47,7 @@
 #define TDH_VP_WR			43
 #define TDH_SYS_CONFIG			45
 #define TDH_SYS_SHUTDOWN		52
+#define TDH_SYS_UPDATE			53
 #define TDH_SYS_DISABLE			69
 
 /*
@@ -110,5 +111,6 @@ struct tdmr_info_list {
 };
 
 int tdx_module_shutdown(void);
+int tdx_module_run_update(void);
 
 #endif