linux-kernel - [RFC PATCH 15/20] x86/virt/seamldr: Handle TD-Preserving update failures

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Message-ID: <20250523095322.88774-16-chao.gao@intel.com>
Date: Fri, 23 May 2025 02:52:38 -0700
From: Chao Gao <chao.gao@...el.com>
To: linux-coco@...ts.linux.dev,
	x86@...nel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	pbonzini@...hat.com,
	eddie.dong@...el.com,
	kirill.shutemov@...el.com,
	dave.hansen@...el.com,
	dan.j.williams@...el.com,
	kai.huang@...el.com,
	isaku.yamahata@...el.com,
	elena.reshetova@...el.com,
	rick.p.edgecombe@...el.com,
	Chao Gao <chao.gao@...el.com>,
	Farrah Chen <farrah.chen@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 15/20] x86/virt/seamldr: Handle TD-Preserving update failures

Failure encounterred after the module shutdown are unrecoverable. All
subsequent SEAMCALLs will fail and TDs will be killed.

Report the error through sysfs attributes and log a message to clarify that
SEAMCALL errors are expected in this situation.

Signed-off-by: Chao Gao <chao.gao@...el.com>
Tested-by: Farrah Chen <farrah.chen@...el.com>
---
 arch/x86/virt/vmx/tdx/seamldr.c | 15 ++++++++++++++-
 arch/x86/virt/vmx/tdx/tdx.c     | 13 +++++++++++++
 arch/x86/virt/vmx/tdx/tdx.h     |  1 +
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 1ecb5d3088af..a18df08a5528 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -278,6 +278,14 @@ static void ack_state(void)
 	}
 }
 
+static void print_update_failure_message(void)
+{
+	static atomic_t printed = ATOMIC_INIT(0);
+
+	if (atomic_inc_return(&printed) == 1)
+		pr_err("update failed, SEAMCALLs will report failure until TDs killed\n");
+}
+
 /*
  * See multi_cpu_stop() from where this multi-cpu state-machine was
  * adopted, and the rationale for touch_nmi_watchdog()
@@ -314,8 +322,13 @@ static int do_seamldr_install_module(void *params)
 				break;
 			}
 
-			if (ret)
+			if (ret) {
 				atomic_inc(&tdp_data.failed);
+				if (curstate >= TDP_CPU_INSTALL) {
+					tdx_module_set_error();
+					print_update_failure_message();
+				}
+			}
 			ack_state();
 		} else {
 			touch_nmi_watchdog();
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 4cdeec0a4128..331c86eeddcf 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1102,6 +1102,13 @@ static ssize_t version_show(struct device *dev, struct device_attribute *attr,
 {
 	const struct tdx_sys_info_versions *v = &tdx_sysinfo.versions;
 
+	/*
+	 * Inform userspace that the TDX module isn't in a usable state,
+	 * possibly due to a failed update.
+	 */
+	if (tdx_module_status != TDX_MODULE_INITIALIZED)
+		return -ENXIO;
+
 	return sysfs_emit(buf, "%u.%u.%u\n", v->major_version,
 					     v->minor_version,
 					     v->update_version);
@@ -1377,6 +1384,12 @@ int tdx_module_shutdown(void)
 	return ret;
 }
 
+void tdx_module_set_error(void)
+{
+	/* Called from stop_machine(). no need to hold tdx_module_lock */
+	tdx_module_status = TDX_MODULE_ERROR;
+}
+
 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 3830dee4da91..ed3d74c991f6 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -125,5 +125,6 @@ struct tdmr_info_list {
 int seamldr_prerr(u64 fn, struct tdx_module_args *args);
 
 int tdx_module_shutdown(void);
+void tdx_module_set_error(void);
 
 #endif
-- 
2.47.1