linux-kernel - [PATCH v3 12/26] x86/virt/seamldr: Verify availability of slots for TDX Module updates

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Message-ID: <20260123145645.90444-13-chao.gao@intel.com>
Date: Fri, 23 Jan 2026 06:55:20 -0800
From: Chao Gao <chao.gao@...el.com>
To: linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	x86@...nel.org
Cc: reinette.chatre@...el.com,
	ira.weiny@...el.com,
	kai.huang@...el.com,
	dan.j.williams@...el.com,
	yilun.xu@...ux.intel.com,
	sagis@...gle.com,
	vannapurve@...gle.com,
	paulmck@...nel.org,
	nik.borisov@...e.com,
	zhenzhong.duan@...el.com,
	seanjc@...gle.com,
	rick.p.edgecombe@...el.com,
	kas@...nel.org,
	dave.hansen@...ux.intel.com,
	vishal.l.verma@...el.com,
	Chao Gao <chao.gao@...el.com>,
	Farrah Chen <farrah.chen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v3 12/26] x86/virt/seamldr: Verify availability of slots for TDX Module updates

The CPU keeps track of TCB versions for each TDX Module that has been
loaded. Since this tracking database has finite capacity, there's a maximum
number of module updates that can be performed. After each successful
update, the number reduces by one. Once it reaches zero, further updates
will fail until next reboot.

Before updating the TDX Module, ensure that the limit on TDX Module updates
has not been exceeded to prevent update failures in a later phase where TDs
have to be killed.

Signed-off-by: Chao Gao <chao.gao@...el.com>
Tested-by: Farrah Chen <farrah.chen@...el.com>
---
 arch/x86/virt/vmx/tdx/seamldr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 88388aa0fb5f..d1d4f96c4963 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -83,6 +83,14 @@ EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
  */
 int seamldr_install_module(const u8 *data, u32 size)
 {
+	const struct seamldr_info *info = seamldr_get_info();
+
+	if (!info)
+		return -EIO;
+
+	if (!info->num_remaining_updates)
+		return -ENOSPC;
+
 	if (!is_vmalloc_addr(data))
 		return -EINVAL;
 
-- 
2.47.3