On 2/12/21 6:38 AM, Rob Herring wrote:
On Thu, Feb 11, 2021 at 7:17 PM Lakshmi Ramasubramanian
<nramas@xxxxxxxxxxxxxxxxxxx> wrote:
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?
Yes, I guess so. But please define the param as extra size, not total
size. The kernel command line size addition can be in the common code.
Will do. Just to clarify -
The common code will do:
fdt_totalsize(initial_boot_params) + strlen(cmdline) + extra_fdt_size
The caller will pass "extra_fdt_size"
ARM64 => 4KB
PPC64 => fdt_totalsize(initial_boot_params) - which will be updated when
the patch Thiago had referred to is merged.
The above change is also going to conflict, so I think this may have
to wait. Or I'll take the common and arm bits and powerpc can be
converted next cycle (or after the merge window).
thanks.
-lakshmi
