Re: [PATCH] of/kexec: save pa of initial_boot_params for arm64 and use it at kexec

[Rob Herring]

On Thu, Oct 03, 2024 at 12:38:40PM +0100, Usama Arif wrote:
>  __pa() is only intended to be used for linear map addresses and using
> it for initial_boot_params which is in fixmap for arm64 will give an
> incorrect value. Hence stash the physical address when it is known at
> boot time and use it at kexec time instead of converting the virtual
> address using __pa().
> 
> Reported-by: Breno Leitao <leitao@xxxxxxxxxx>
> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
> Fixes: ac10be5cdbfa ("arm64: Use common of_kexec_alloc_and_setup_fdt()")
> ---
>  arch/arm64/kernel/setup.c | 8 ++++++++
>  drivers/of/fdt.c          | 6 ++++++
>  drivers/of/kexec.c        | 8 ++++++--
>  include/linux/of_fdt.h    | 2 ++
>  4 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index b22d28ec8028..a4d96f5e2e05 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -194,6 +194,14 @@ static void __init setup_machine_fdt(phys_addr_t dt_phys)
>  	/* Early fixups are done, map the FDT as read-only now */
>  	fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL_RO);
>  
> +	/*
> +	 * Save dt_phys address so that it can be used later for kexec. This
> +	 * is done as __pa() is only intended to be used for linear map addresses
> +	 * and using it for initial_boot_params which is in fixmap will give an
> +	 * incorrect value.
> +	 */
> +	set_initial_boot_params_pa(dt_phys);

No new arch->dt functions please. If we need to save off the PA, then do 
that when we set initial_boot_params.

Rob