Re: [PATCH 5/5] riscv/efi_stub: Support for 64bit boot-hartid

Ard Biesheuvel
2022-05-25T15:49:15Z

On Wed, 25 May 2022 at 17:11, Sunil V L <sunilvl@ventanamicro.com> wrote:
>
> The boot-hartid can be a 64bit value on RV64 platforms. Currently,
> the "boot-hartid" in DT is assumed to be 32bit only. This patch
> detects the size of the "boot-hartid" and uses 32bit or 64bit
> FDT reads appropriately.
>
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
> drivers/firmware/efi/libstub/riscv-stub.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
> index 9e85e58d1f27..d748533f1329 100644
> --- a/drivers/firmware/efi/libstub/riscv-stub.c
> +++ b/drivers/firmware/efi/libstub/riscv-stub.c
> @@ -29,7 +29,7 @@ static int get_boot_hartid_from_fdt(void)
> {
> const void *fdt;
> int chosen_node, len;
> - const fdt32_t *prop;
> + const void *prop;
>
> fdt = get_efi_config_table(DEVICE_TREE_GUID);
> if (!fdt)
> @@ -40,10 +40,16 @@ static int get_boot_hartid_from_fdt(void)
> return -EINVAL;
>
> prop = fdt_getprop((void *)fdt, chosen_node, "boot-hartid", &len);
> - if (!prop || len != sizeof(u32))
> + if (!prop)
> + return -EINVAL;
> +
> + if (len == sizeof(u32))
> + hartid = (unsigned long) fdt32_to_cpu(*(fdt32_t *)prop);
> + else if (len == sizeof(u64))
> + hartid = (unsigned long) fdt64_to_cpu(*(fdt64_t *)prop);

Does RISC-V care about alignment? A 64-bit quantity is not guaranteed
to appear 64-bit aligned in the DT, and the cast violates C alignment
rules, so this should probably used get_unaligned_be64() or something
like that.

> + else
> return -EINVAL;
>
> - hartid = fdt32_to_cpu(*prop);
> return 0;
> }
>
> --
> 2.25.1
>