Re: [PATCH] arm[64]/memremap: fix arch_memremap_can_ram_remap()

Catalin Marinas
2025-04-14T13:49:53Z

Please cc the maintainers and the original contributor of the commit you
are fixing, otherwise the patch may not be noticed.

On Mon, Apr 14, 2025 at 08:32:19AM -0500, Ross Stutterheim wrote:
> commit 260364d112bc ("arm[64]/memremap: don't abuse pfn_valid() to ensure
> presence of linear map") added the definition of
> arch_memremap_can_ram_remap() for arm[64] specific filtering of what pages
> can be used from the linear mapping. memblock_is_map_memory() was called
> with the pfn of the address given to arch_memremap_can_ram_remap();
> however, memblock_is_map_memory() expects to be given an address, not a
> pfn.
>
> This results in calls to memremap() returning a newly mapped area when
> it should return an address in the existing linear mapping.
>
> Fix this by removing the address to pfn translation and pass the
> address directly.
>
> Fixes: 260364d112bc ("arm[64]/memremap: don't abuse pfn_valid() to ensure presence of linear map")
> Signed-off-by: Ross Stutterheim <ross.stutterheim@garmin.com>
> ---
> arch/arm/mm/ioremap.c | 4 +---
> arch/arm64/mm/ioremap.c | 4 +---
> 2 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
> index 748698e91a4b..27e64f782cb3 100644
> --- a/arch/arm/mm/ioremap.c
> +++ b/arch/arm/mm/ioremap.c
> @@ -515,7 +515,5 @@ void __init early_ioremap_init(void)
> bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
> unsigned long flags)
> {
> - unsigned long pfn = PHYS_PFN(offset);
> -
> - return memblock_is_map_memory(pfn);
> + return memblock_is_map_memory(offset);
> }

This indeed needs fixing.

> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
> index 10e246f11271..48c38c986b95 100644
> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -51,7 +51,5 @@ void __init early_ioremap_init(void)
> bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
> unsigned long flags)
> {
> - unsigned long pfn = PHYS_PFN(offset);
> -
> - return pfn_is_map_memory(pfn);
> + return pfn_is_map_memory(offset);

This is already correct.

--
Catalin