[PATCH v2 10/21] x86/virt/seamldr: Verify availability of slots for TDX Module updates

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

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@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.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 b9e025d0f0bc..9f7d96ca8b2f 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -74,6 +74,14 @@ EXPORT_SYMBOL_GPL_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;
+
 	guard(cpus_read_lock)();
 	if (!cpumask_equal(cpu_online_mask, cpu_present_mask)) {
 		pr_err("Cannot update TDX module if any CPU is offline\n");
-- 
2.47.3