Re: [PATCH] efi/libstub/arm*: Set default address and size cells values for an empty dtb

Mark Rutland
2017-02-07T18:15:54Z

Hi,

On Tue, Feb 07, 2017 at 10:59:50AM -0700, Jeffrey Hugo wrote:
> From: Sameer Goel <sgoel-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
>
> 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.

What values are being read by the tools, and for what purpose?

Are they extracting data from the DTB, or is this part of inserting a
new property?

Why does this adversely affect ACPI?

> Change-Id: Ie7f3637e375bd6631c6bda1f7b3c9003765ff4a5

Please remove this kind of tags from upstream patches. It's irrelevant.

> Signed-off-by: Sameer Goel <sgoel-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> Signed-off-by: Jeffrey Hugo <jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> ---
> drivers/firmware/efi/libstub/fdt.c | 38 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index 921dfa0..def5c9c 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -16,6 +16,34 @@
>
> #include "efistub.h"
>
> +#define EFI_DT_ADDR_CELLS_DEFAULT 2
> +#define EFI_DT_SIZE_CELLS_DEFAULT 2
> +
> +static void fdt_update_cell_size(efi_system_table_t *sys_table, void *fdt)
> +{
> + int offset;
> + int status;
> +
> + offset = fdt_path_offset(fdt, "/");
> + /* Set the #address-cells and #size-cells values for an empty tree */
> +
> + status = fdt_setprop_u32(fdt, offset, "#address-cells",
> + EFI_DT_ADDR_CELLS_DEFAULT);
> + if (status) {
> + pr_efi(sys_table,
> + "Failed to set #address-cells for empty dtb\n");
> + return;
> + }
> +
> + status = fdt_setprop_u32(fdt, offset, "#size-cells",
> + EFI_DT_SIZE_CELLS_DEFAULT);
> + if (status) {
> + pr_efi(sys_table,
> + "Failed to set #size-cells for empty dtb\n");
> + return;
> + }
> +}

We don't seem to log anything for most other failures within
update_fdt() where this is called.

Are these really much more special?

> static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
> unsigned long orig_fdt_size,
> void *fdt, int new_fdt_size, char *cmdline_ptr,
> @@ -44,8 +72,16 @@ static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
>
> if (orig_fdt)
> status = fdt_open_into(orig_fdt, fdt, new_fdt_size);
> - else
> + else {

Nit: if one side of an if-else has braces, the other should too per the
usual kernel coding style.

Thanks,
Mark.