linux-kernel - Re: [PATCH v2] of/fdt: add dt_phys arg to early_init_dt_scan and early_init_dt

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Message-ID: <20241028154054.GE2484@willie-the-truck>
Date: Mon, 28 Oct 2024 15:40:55 +0000
From: Will Deacon <will@...nel.org>
To: Usama Arif <usamaarif642@...il.com>
Cc: robh@...nel.org, mark.rutland@....com, leitao@...ian.org,
	catalin.marinas@....com, tglx@...utronix.de, chris@...kel.net,
	saravanak@...gle.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	kexec@...ts.infradead.org, loongarch@...ts.linux.dev,
	linux-sh@...r.kernel.org, linux-riscv@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-openrisc@...r.kernel.org,
	linux-mips@...r.kernel.org, linux-csky@...r.kernel.org
Subject: Re: [PATCH v2] of/fdt: add dt_phys arg to early_init_dt_scan and
 early_init_dt_verify

On Wed, Oct 23, 2024 at 06:14:26PM +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 save the physical address when it is known at
> boot time when calling early_init_dt_scan for arm64 and use it at kexec
> time instead of converting the virtual address using __pa().
> 
> Reported-by: Breno Leitao <leitao@...ian.org>
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Usama Arif <usamaarif642@...il.com>
> Fixes: ac10be5cdbfa ("arm64: Use common of_kexec_alloc_and_setup_fdt()")
> ---
> v1 -> 2:
> - pass dt_phys in early_init_dt_scan instead of creating
>   anorther arch->dt function (Rob Herring)
> ---
>  arch/arc/kernel/devtree.c              |  2 +-
>  arch/arm/kernel/devtree.c              |  2 +-
>  arch/arm64/kernel/setup.c              |  6 +++++-
>  arch/csky/kernel/setup.c               |  4 ++--
>  arch/loongarch/kernel/setup.c          |  2 +-
>  arch/microblaze/kernel/prom.c          |  2 +-
>  arch/mips/kernel/prom.c                |  2 +-
>  arch/mips/kernel/relocate.c            |  2 +-
>  arch/nios2/kernel/prom.c               |  4 ++--
>  arch/openrisc/kernel/prom.c            |  2 +-
>  arch/powerpc/kernel/dt_cpu_ftrs.c      |  2 +-
>  arch/powerpc/kernel/prom.c             |  2 +-
>  arch/powerpc/platforms/pseries/plpks.c |  2 +-
>  arch/riscv/kernel/setup.c              |  2 +-
>  arch/sh/kernel/setup.c                 |  2 +-
>  arch/um/kernel/dtb.c                   |  2 +-
>  arch/x86/kernel/devicetree.c           |  2 +-
>  arch/xtensa/kernel/setup.c             |  2 +-
>  drivers/of/fdt.c                       | 14 ++++++++------
>  drivers/of/kexec.c                     |  2 +-
>  include/linux/of_fdt.h                 |  5 +++--
>  21 files changed, 36 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/arc/kernel/devtree.c b/arch/arc/kernel/devtree.c
> index 4c9e61457b2f..cc6ac7d128aa 100644
> --- a/arch/arc/kernel/devtree.c
> +++ b/arch/arc/kernel/devtree.c
> @@ -62,7 +62,7 @@ const struct machine_desc * __init setup_machine_fdt(void *dt)
>  	const struct machine_desc *mdesc;
>  	unsigned long dt_root;
>  
> -	if (!early_init_dt_scan(dt))
> +	if (!early_init_dt_scan(dt, __pa(dt)))
>  		return NULL;
>  
>  	mdesc = of_flat_dt_match_machine(NULL, arch_get_next_mach);
> diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
> index fdb74e64206a..3b78966e750a 100644
> --- a/arch/arm/kernel/devtree.c
> +++ b/arch/arm/kernel/devtree.c
> @@ -200,7 +200,7 @@ const struct machine_desc * __init setup_machine_fdt(void *dt_virt)
>  
>  	mdesc_best = &__mach_desc_GENERIC_DT;
>  
> -	if (!dt_virt || !early_init_dt_verify(dt_virt))
> +	if (!dt_virt || !early_init_dt_verify(dt_virt, __pa(dt_virt)))
>  		return NULL;
>  
>  	mdesc = of_flat_dt_match_machine(mdesc_best, arch_get_next_mach);
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index b22d28ec8028..177262739c49 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -175,7 +175,11 @@ static void __init setup_machine_fdt(phys_addr_t dt_phys)
>  	if (dt_virt)
>  		memblock_reserve(dt_phys, size);
>  
> -	if (!dt_virt || !early_init_dt_scan(dt_virt)) {
> +	/*
> +	 * dt_virt is a fixmap address, hence __pa(dt_virt) can't be used.
> +	 * Pass dt_phys directly.
> +	 */
> +	if (!dt_virt || !early_init_dt_scan(dt_virt, dt_phys)) {

nit: It looks like early_init_dt_verify() will now return false if
!dt_virt, so we can drop the additional check here.

Will