Messages in this thread | | | Subject | Re: [PATCH v17 02/10] of: Add a common kexec FDT setup function | From | Lakshmi Ramasubramanian <> | Date | Thu, 11 Feb 2021 17:17:56 -0800 |
| |
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
| |