[PATCH v4 18/24] x86/virt/tdx: Restore TDX Module state

[Chao Gao]

TDX Module state was packed as handoff data during module shutdown. After
per-CPU initialization, the new module can restore TDX Module state from
handoff data to preserve running TDs.

Once the restoration is done, the TDX Module update is complete, which
means the new module is ready to handle requests from the host and guests.

Implement the new TDH.SYS.UPDATE SEAMCALL to restore TDX Module state
and invoke it for one CPU.

Note that Intel® Trust Domain Extensions (Intel® TDX) Module Base
Architecture Specification, Revision 348549-007, Chapter 4.5.5 states:

  If TDH.SYS.UPDATE returns an error, then the host VMM can continue
  with the non-update sequence (TDH.SYS.CONFIG, 15 TDH.SYS.KEY.CONFIG
  etc.). In this case all existing TDs are lost. Alternatively, the host
  VMM can request the P-SEAMLDR to update to another TDX Module. If that
  update is successful, existing TDs are preserved

The two alternative error handling approaches are not implemented due to
their complexity and unclear benefits.

Also note that 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 doesn't need to provide its location, format etc.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
---
v3:
 - use seamcall_prerr() rather than raw seamcall() [Binbin]
 - use pr_err() to print error message [Binbin]
---
 arch/x86/virt/vmx/tdx/seamldr.c |  5 +++++
 arch/x86/virt/vmx/tdx/tdx.c     | 16 ++++++++++++++++
 arch/x86/virt/vmx/tdx/tdx.h     |  2 ++
 3 files changed, 23 insertions(+)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index e29e6094c80b..0ca802234695 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -201,6 +201,7 @@ enum tdp_state {
 	TDP_SHUTDOWN,
 	TDP_CPU_INSTALL,
 	TDP_CPU_INIT,
+	TDP_RUN_UPDATE,
 	TDP_DONE,
 };
 
@@ -264,6 +265,10 @@ static int do_seamldr_install_module(void *seamldr_params)
 			case TDP_CPU_INIT:
 				ret = tdx_cpu_enable();
 				break;
+			case TDP_RUN_UPDATE:
+				if (primary)
+					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 a1193efc1156..a8adb2c97e2f 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1202,6 +1202,22 @@ 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) {
+		pr_err("TDX-Module update failed (%d)\n", ret);
+		tdx_module_status = TDX_MODULE_ERROR;
+		return ret;
+	}
+
+	tdx_module_status = TDX_MODULE_INITIALIZED;
+	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 1c4da9540ae0..0887debfd139 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
 
 /*
  * SEAMCALL leaf:
@@ -120,5 +121,6 @@ struct tdmr_info_list {
 };
 
 int tdx_module_shutdown(void);
+int tdx_module_run_update(void);
 
 #endif
-- 
2.47.3