@@ -15,6 +15,7 @@
#include <linux/acpi.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
+#include <linux/cc_platform.h>
#include "internal.h"
@@ -291,6 +292,17 @@ static int acpi_memory_device_add(struct acpi_device *device,
if (!device)
return -EINVAL;
+ /*
+ * If the confidential computing platform doesn't support ACPI
+ * memory hotplug, the BIOS should never deliver such event to
+ * the kernel. Report ACPI CPU hot-add as a BIOS bug and ignore
+ * the memory device.
+ */
+ if (cc_platform_has(CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED)) {
+ dev_err(&device->dev, "[BIOS bug]: Platform doesn't support ACPI memory hotplug. New memory device ignored.\n");
+ return -EINVAL;
+ }
+
mem_device = kzalloc(sizeof(struct acpi_memory_device), GFP_KERNEL);
if (!mem_device)
return -ENOMEM;
@@ -334,6 +346,17 @@ static void acpi_memory_device_remove(struct acpi_device *device)
if (!device || !acpi_driver_data(device))
return;
+ /*
+ * The confidential computing platform is broken if ACPI memory
+ * hot-removal isn't supported but it happened anyway. Assume
+ * it is not guaranteed that the kernel can continue to work
+ * normally. Just BUG().
+ */
+ if (cc_platform_has(CC_ATTR_ACPI_CPU_HOTPLUG_DISABLED)) {
+ dev_err(&device->dev, "Platform doesn't support ACPI memory hotplug. BUG().\n");
+ BUG();
+ }
+
mem_device = acpi_driver_data(device);
acpi_memory_remove_memory(mem_device);
acpi_memory_device_free(mem_device);
@@ -93,6 +93,17 @@ enum cc_attr {
* Examples include TDX platform.
*/
CC_ATTR_ACPI_CPU_HOTPLUG_DISABLED,
+
+ /**
+ * @CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED: ACPI memory hotplug is
+ * not supported.
+ *
+ * The platform/os is running does not support ACPI memory
+ * hotplug.
+ *
+ * Examples include TDX platform.
+ */
+ CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED,
};
#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
Platforms with confidential computing technology may not support ACPI memory hotplug when such technology is enabled by the BIOS. Examples include Intel platforms which support Intel Trust Domain Extensions (TDX). If the kernel ever receives ACPI memory hotplug event, it is likely a BIOS bug. For ACPI memory hot-add, the kernel should speak out this is a BIOS bug and reject the new memory. For hot-removal, for simplicity just assume the kernel cannot continue to work normally, and just BUG(). Add a new attribute CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED to indicate the platform doesn't support ACPI memory hotplug, so that kernel can handle ACPI memory hotplug events for such platform. In acpi_memory_device_{add|remove}(), add early check against this attribute and handle accordingly if it is set. Signed-off-by: Kai Huang <kai.huang@intel.com> --- drivers/acpi/acpi_memhotplug.c | 23 +++++++++++++++++++++++ include/linux/cc_platform.h | 11 +++++++++++ 2 files changed, 34 insertions(+)