linux-kernel - Re: [PATCH] riscv: Remove redundant restriction on memory size

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Date: Mon, 1 Jul 2024 14:21:11 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Stuart Menefy <stuart.menefy@...asip.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: Remove redundant restriction on memory size

Hi Stuart,

On 24/06/2024 14:17, Stuart Menefy wrote:
> The original reason for reserving the top 4GiB of the direct map
> (space for modules/BPF/kernel) hasn't applied since the address
> map was reworked for KASAN.
>
> Signed-off-by: Stuart Menefy <stuart.menefy@...asip.com>
> ---
>   arch/riscv/mm/init.c | 8 +-------
>   1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 7e25606f858a..3998d1ca369c 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1130,13 +1130,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   				0UL : PAGE_OFFSET - kernel_map.phys_addr;
>   	kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr;
>   
> -	/*
> -	 * The default maximal physical memory size is KERN_VIRT_SIZE for 32-bit
> -	 * kernel, whereas for 64-bit kernel, the end of the virtual address
> -	 * space is occupied by the modules/BPF/kernel mappings which reduces
> -	 * the available size of the linear mapping.
> -	 */
> -	memory_limit = KERN_VIRT_SIZE - (IS_ENABLED(CONFIG_64BIT) ? SZ_4G : 0);
> +	memory_limit = KERN_VIRT_SIZE;
>   
>   	/* Sanity check alignment and size */
>   	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);


I somehow totally missed this one, I guess this is the third fix you 
mentioned earlier right?

This is correct so you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex