[PATCH] RISC-V: mm: Fix set_satp_mode() for platform not having Sv57

[潘庆霖]

Hi Anup,

> 
> When Sv57 is not available the satp.MODE test in set_satp_mode() will
> fail and lead to pgdir re-programming for Sv48. The pgdir re-programming
> will fail as well due to pre-existing pgdir entry used for Sv57 and as
> a result kernel fails to boot on RISC-V platform not having Sv57.
> 
> To fix above issue, we should clear the pgdir memory in set_satp_mode()
> before re-programming.
> 
> Fixes: 011f09d12052 ("riscv: mm: Set sv57 on defaultly")
> Reported-by: Mayuresh Chitale <mchitale at ventanamicro.com>
> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> ---
>  arch/riscv/mm/init.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 9535bea8688c..b0793dc0c291 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -718,6 +718,7 @@ static __init void set_satp_mode(void)
>  		if (!check_l4) {
>  			disable_pgtable_l5();
>  			check_l4 = true;
> +			memset(early_pg_dir, 0, PAGE_SIZE);
>  			goto retry;
>  		}
>  		disable_pgtable_l4();
> -- 


I find it that the set_satp_mode function is in .init.text section which begins at 0x80800000.
And its pgd_index in both Sv48 and Sv57 will be 0. So it may not be necessary to clear the 
early_pg_dir when the kernel find Sv57 is not supported? And may I get the steps of reproduction
from you?
 
Yours,
Qinglin
</apatel at ventanamicro.com></mchitale at ventanamicro.com>