On Wed, Jun 22, 2022 at 1:16 PM Kai Huang <kai.huang@xxxxxxxxx> wrote: > > 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@xxxxxxxxx> > --- > drivers/acpi/acpi_memhotplug.c | 23 +++++++++++++++++++++++ > include/linux/cc_platform.h | 10 ++++++++++ > 2 files changed, 33 insertions(+) > > diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c > index 24f662d8bd39..94d6354ea453 100644 > --- a/drivers/acpi/acpi_memhotplug.c > +++ b/drivers/acpi/acpi_memhotplug.c > @@ -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)) { Same comment as for the acpi_processor driver: this will affect the initialization too and it would be cleaner to reset the .hotplug.enabled flag of the scan handler. > + 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); > diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h > index 9ce9256facc8..b831c24bd7f6 100644 > --- a/include/linux/cc_platform.h > +++ b/include/linux/cc_platform.h > @@ -93,6 +93,16 @@ 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 does not support ACPI memory hotplug. > + * > + * Examples include TDX platform. > + */ > + CC_ATTR_ACPI_MEMORY_HOTPLUG_DISABLED, > }; > > #ifdef CONFIG_ARCH_HAS_CC_PLATFORM > -- > 2.36.1 >