[PATCH v2 14/21] x86/virt/seamldr: Shut down the current TDX module

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

TDX Module 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 SEAMCALL on one CPU to perform the shutdown.
This SEAMCALL 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 as new modules likely have
higher hand-off version.

Generate changes to tdx_global_metadata.{hc} by following the
instructions detailed in [1], after adding the following section to the
tdx.py script:

    "handoff": [
       "MODULE_HV",
    ],

Manually add a check in get_tdx_sys_info_handoff() to guard reading the
"module_hv" field with TDX Module update support as otherwise the field
doesn't exist.

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]
---
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             | 10 ++++++++++
 arch/x86/virt/vmx/tdx/tdx.c                 | 16 ++++++++++++++++
 arch/x86/virt/vmx/tdx/tdx.h                 |  3 +++
 arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 13 +++++++++++++
 5 files changed, 47 insertions(+)

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 fca558b90f72..b9daf11e1064 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -19,6 +19,7 @@
 #include <asm/seamldr.h>
 
 #include "seamcall.h"
+#include "tdx.h"
 
 /* P-SEAMLDR SEAMCALL leaf function */
 #define P_SEAMLDR_INFO			0x8000000000000000
@@ -229,6 +230,7 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
  */
 enum tdp_state {
 	TDP_START,
+	TDP_SHUTDOWN,
 	TDP_DONE,
 };
 
@@ -269,8 +271,12 @@ 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();
@@ -279,6 +285,10 @@ static int do_seamldr_install_module(void *params)
 		if (newstate != curstate) {
 			curstate = newstate;
 			switch (curstate) {
+			case TDP_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 b367bb1d94ed..89b51e270274 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1191,6 +1191,22 @@ int tdx_enable(void)
 }
 EXPORT_SYMBOL_GPL(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 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 as new modules likely have higher
+	 * hand-off version.
+	 */
+	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 0454124803f3..3fdd5cbc21d8 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 (tdx_supports_runtime_update(&tdx_sysinfo) &&
+	    !(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;
 }
-- 
2.47.3