[PATCH v2 09/21] x86/virt/seamldr: Block TDX Module updates if any CPU is offline

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

P-SEAMLDR requires every CPU to call the SEAMLDR.INSTALL SEAMCALL during
updates.  So, every CPU should be online.

Check if all CPUs are online and abort the update if any CPU is offline at
the very beginning. Without this check, P-SEAMLDR will report failure at a
later phase where the old TDX module is gone and TDs have to be killed.

Signed-off-by: Chao Gao <chao.gao@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 69c059194c61..b9e025d0f0bc 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -6,6 +6,8 @@
  */
 #define pr_fmt(fmt)	"seamldr: " fmt
 
+#include <linux/cpuhplock.h>
+#include <linux/cpumask.h>
 #include <linux/irqflags.h>
 #include <linux/types.h>
 
@@ -72,6 +74,12 @@ EXPORT_SYMBOL_GPL_FOR_MODULES(seamldr_get_info, "tdx-host");
 
 int seamldr_install_module(const u8 *data, u32 size)
 {
+	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");
+		return -EBUSY;
+	}
+
 	/* TODO: Update TDX Module here */
 	return 0;
 }
-- 
2.47.3