On 2/11/21 5:09 PM, Thiago Jung Bauermann wrote:
There's actually a complication that I just noticed and needs to be addressed. More below.
<...>
+ +/* + * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree + * + * @image: kexec image being loaded. + * @initrd_load_addr: Address where the next initrd will be loaded. + * @initrd_len: Size of the next initrd, or 0 if there will be none. + * @cmdline: Command line for the next kernel, or NULL if there will + * be none. + * + * Return: fdt on success, or NULL errno on error. + */ +void *of_kexec_alloc_and_setup_fdt(const struct kimage *image, + unsigned long initrd_load_addr, + unsigned long initrd_len, + const char *cmdline) +{ + void *fdt; + int ret, chosen_node; + const void *prop; + unsigned long fdt_size; + + fdt_size = fdt_totalsize(initial_boot_params) + + (cmdline ? strlen(cmdline) : 0) + + FDT_EXTRA_SPACE;Just adding 4 KB to initial_boot_params won't be enough for crash kernels on ppc64. The current powerpc code doubles the size of initial_boot_params (which is normally larger than 4 KB) and even that isn't enough. A patch was added to powerpc/next today which uses a more precise (but arch-specific) formula: https://lore.kernel.org/linuxppc-dev/161243826811.119001.14083048209224609814.stgit@hbathini/ So I believe we need a hook here where architectures can provide their own specific calculation for the size of the fdt. Perhaps a weakly defined function providing a default implementation which an arch-specific file can override (a la arch_kexec_kernel_image_load())? Then the powerpc specific hook would be the kexec_fdt_totalsize_ppc64() function from the patch I linked above.
Do you think it'd better to add "fdt_size" parameter to of_kexec_alloc_and_setup_fdt() so that the caller can provide the desired FDT buffer size?
thanks, -lakshmi
