[RFC PATCH 12/20] x86/virt/seamldr: Shut down the current TDX module

[Chao Gao <chao.gao@intel.com>]

TD-Preserving updates request shutting down the existing TDX module.
During this shutdown, the module generates hand-off data, which captures
the module's states essential for preserving running TDs. The new TDX
module can utilize this hand-off data to establish its states.

Invoke the TDH_SYS_SHUTDOWN API on one CPU to perform the shutdown. This
API requires a hand-off module version. Use the module's own hand-off
version, as it is the highest version the module can produce and is more
likely to be compatible with new modules.

Changes to tdx_global_metadata.{hc} are auto-generated by following the
instructions detailed in [1], after adding the following section to the
tdx.py script:

    "handoff": [
       "MODULE_HV",
    ],

Add a check to ensure that module_hv is guarded by the TDX module's
support for TD-Preserving.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Link: https://lore.kernel.org/kvm/20250226181453.2311849-12-pbonzini@redhat.com/ [1]
---
 arch/x86/include/asm/tdx_global_metadata.h  |  5 +++++
 arch/x86/virt/vmx/tdx/seamldr.c             | 11 +++++++++++
 arch/x86/virt/vmx/tdx/tdx.c                 | 18 ++++++++++++++++++
 arch/x86/virt/vmx/tdx/tdx.h                 |  4 ++++
 arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 13 +++++++++++++
 5 files changed, 51 insertions(+)

diff --git a/arch/x86/include/asm/tdx_global_metadata.h b/arch/x86/include/asm/tdx_global_metadata.h
index ce0370f4a5b9..a2011a3575ff 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_versions versions;
 	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 9d0d37a92bfd..11c0c5a93c32 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -241,6 +241,7 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
 
 enum tdp_state {
 	TDP_START,
+	TDP_SHUTDOWN,
 	TDP_DONE,
 };
 
@@ -281,8 +282,12 @@ static void ack_state(void)
 static int do_seamldr_install_module(void *params)
 {
 	enum tdp_state newstate, curstate = TDP_START;
+	int cpu = smp_processor_id();
+	bool primary;
 	int ret = 0;
 
+	primary = !!(cpumask_first(cpu_online_mask) == cpu);
+
 	do {
 		/* Chill out and ensure we re-read tdp_data. */
 		cpu_relax();
@@ -291,6 +296,12 @@ static int do_seamldr_install_module(void *params)
 		if (newstate != curstate) {
 			curstate = newstate;
 			switch (curstate) {
+			case TDP_SHUTDOWN:
+				if (!primary)
+					break;
+
+				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 22ffc15b4299..fa6b3f1eb197 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -295,6 +295,11 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
 	return 0;
 }
 
+static bool tdx_has_td_preserving(void)
+{
+	return tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_TD_PRESERVING;
+}
+
 #include "tdx_global_metadata.c"
 
 static int check_features(struct tdx_sys_info *sysinfo)
@@ -1341,6 +1346,19 @@ int tdx_enable(void)
 }
 EXPORT_SYMBOL_GPL(tdx_enable);
 
+int tdx_module_shutdown(void)
+{
+	struct tdx_module_args args = {};
+
+	/*
+	 * Shut down TDX module and prepare handoff data for the next TDX module.
+	 * Following a successful TDH_SYS_SHUTDOWN, further TDX module APIs will
+	 * fail.
+	 */
+	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 48c0a850c621..3830dee4da91 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -48,6 +48,7 @@
 #define TDH_PHYMEM_PAGE_WBINVD		41
 #define TDH_VP_WR			43
 #define TDH_SYS_CONFIG			45
+#define TDH_SYS_SHUTDOWN		52
 
 /*
  * SEAMCALL leaf:
@@ -87,6 +88,7 @@ struct tdmr_info {
 } __packed __aligned(TDMR_INFO_ALIGNMENT);
 
 /* Bit definitions of TDX_FEATURES0 metadata field */
+#define TDX_FEATURES0_TD_PRESERVING	BIT(1)
 #define TDX_FEATURES0_NO_RBP_MOD	BIT(18)
 
 /*
@@ -122,4 +124,6 @@ struct tdmr_info_list {
 
 int seamldr_prerr(u64 fn, struct tdx_module_args *args);
 
+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 088e5bff4025..a17cbb82e6b8 100644
--- a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
+++ b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
@@ -100,6 +100,18 @@ 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 = 0;
+	u64 val;
+
+	if (!ret && tdx_has_td_preserving() &&
+	    !(ret = read_sys_metadata_field(0x8900000100000000, &val)))
+		sysinfo_handoff->module_hv = val;
+
+	return ret;
+}
+
 static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
 {
 	int ret = 0;
@@ -109,6 +121,7 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
 	ret = ret ?: get_tdx_sys_info_tdmr(&sysinfo->tdmr);
 	ret = ret ?: get_tdx_sys_info_td_ctrl(&sysinfo->td_ctrl);
 	ret = ret ?: get_tdx_sys_info_td_conf(&sysinfo->td_conf);
+	ret = ret ?: get_tdx_sys_info_handoff(&sysinfo->handoff);
 
 	return ret;
 }
-- 
2.47.1