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SubjectRe: [PATCH] riscv: mm: remove the BUG_ON check of mapping the last 4K bytes of memory
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On 1/25/22 16:55, Jisheng Zhang wrote:
> remove the BUG_ON check of mapping the last 4K bytes of the addressable
> memory since "this is true for every kernel actually" as pointed out
> by Alexandre.
>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> Reviewed-by: Alexandre Ghiti <alex@ghiti.fr>
> ---
> arch/riscv/mm/init.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index cf4d018b7d66..8347d0fda8cd 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -811,14 +811,6 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
> BUG_ON((kernel_map.phys_addr % PMD_SIZE) != 0);
>
> -#ifdef CONFIG_64BIT
> - /*
> - * The last 4K bytes of the addressable memory can not be mapped because
> - * of IS_ERR_VALUE macro.
> - */
> - BUG_ON((kernel_map.virt_addr + kernel_map.size) > ADDRESS_SPACE_END - SZ_4K);
> -#endif


This BUG_ON seems pretty legit to me: I re-read the exchanges we had,
and I see that I didn't notice that in your v2, you actually removed the
BUG_ON. So that's my bad, what I meant in the first place was that the
BUG_ON is true for 32-bit and 64-bit kernels actually.

Sorry my RB was not right on this one :(

Alex


> -
> pt_ops_set_early();
>
> /* Setup early PGD for fixmap */

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