On Tue, Feb 7, 2017 at 12:15 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > >> In cases where a device tree is not provided (ie ACPI based system), an >> empty fdt is generated by efistub. Sets the address and size cell values >> in a generated fdt to support 64 bit addressing. >> >> This enables kexec/kdump on Qualcomm Technologies QDF24XX platforms as those >> utilities will read the address/size values from the fdt, and such values >> may exceed the range provided by the 32 bit default. > > The description here doesn't state why this is a problem for ACPI. The patch description could use some work. It's a problem for ACPI because EFI-based systems call typically fdt_create_empty_tree(), which is where the problem lies. The bug is that fdt_create_empty_tree() literally creates an empty tree. By default if a node is missing #address-cells and #size-cells properties, then it's assume that both values are equal to 1, i.e. 32-bit addresses. When update_fdt() in drivers/firmware/efi/libstub/fdt.c creates an empty tree, it then proceeds to inject 64-bit addresses into that tree. When kdump tries to process the address properties, it reads the wrong values because it thinks they are all 32-bit addresses. -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
