[PATCH v2] arm64/mm: use lm_alias() with addresses passed to memblock_free()

[Mark Rutland]

On Thu, Sep 05, 2024 at 04:29:35PM +0100, Joey Gouly wrote:
> The pointer argument to memblock_free() needs to be a linear map address, but
> in mem_init() we pass __init_begin/__init_end, which is a kernel image address.
> 
> This results in warnings when building with CONFIG_DEBUG_VIRTUAL=y:
> 
>     virt_to_phys used for non-linear address: ffff800081270000 (set_reset_devices+0x0/0x10)
>     WARNING: CPU: 0 PID: 1 at arch/arm64/mm/physaddr.c:12 __virt_to_phys+0x54/0x70
>     Modules linked in:
>     CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc6-next-20240905 #5810 b1ebb0ad06653f35ce875413d5afad24668df3f3
>     Hardware name: FVP Base RevC (DT)
>     pstate: 2161402005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
>     pc : __virt_to_phys+0x54/0x70
>     lr : __virt_to_phys+0x54/0x70
>     sp : ffff80008169be20
>     ...
>     Call trace:
>      __virt_to_phys+0x54/0x70
>      memblock_free+0x18/0x30
>      free_initmem+0x3c/0x9c
>      kernel_init+0x30/0x1cc
>      ret_from_fork+0x10/0x20
> 
> Fix this by having mem_init() convert the pointers via lm_alias().
> 
> Fixes: 1db9716d4487 ("arm64/mm: Delete __init region from memblock.reserved")
> Signed-off-by: Joey Gouly <joey.gouly at arm.com>
> Suggested-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Rong Qianfeng <rongqianfeng at vivo.com>

Reviewed-by: Mark Rutland <mark.rutland at arm.com>

Will, are you happy to pick this up? The commit it fixes is queued in
the arm64 for-next/mm branch, and I assume we either want to fix that or
revert it.

Mark.

> ---
>  arch/arm64/mm/init.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 0bde16aadc83..27a32ff15412 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -411,14 +411,16 @@ void __init mem_init(void)
>  
>  void free_initmem(void)
>  {
> -	unsigned long aligned_begin = ALIGN_DOWN((u64)__init_begin, PAGE_SIZE);
> -	unsigned long aligned_end = ALIGN((u64)__init_end, PAGE_SIZE);
> +	void *lm_init_begin = lm_alias(__init_begin);
> +	void *lm_init_end = lm_alias(__init_end);
> +
> +	WARN_ON(!IS_ALIGNED((unsigned long)lm_init_begin, PAGE_SIZE));
> +	WARN_ON(!IS_ALIGNED((unsigned long)lm_init_end, PAGE_SIZE));
>  
>  	/* Delete __init region from memblock.reserved. */
> -	memblock_free((void *)aligned_begin, aligned_end - aligned_begin);
> +	memblock_free(lm_init_begin, lm_init_end - lm_init_begin);
>  
> -	free_reserved_area(lm_alias(__init_begin),
> -			   lm_alias(__init_end),
> +	free_reserved_area(lm_init_begin, lm_init_end,
>  			   POISON_FREE_INITMEM, "unused kernel");
>  	/*
>  	 * Unmap the __init region but leave the VM area in place. This
> -- 
> 2.25.1
>