[V2] riscv: fix pfn_to_virt err in do_page_fault().

[Palmer Dabbelt]

On Fri, 18 Sep 2020 01:55:58 PDT (-0700), liush at allwinnertech.com wrote:
> The argument to pfn_to_virt() should be pfn not the value of CSR_SATP.

Reviewed-by: Palmer Dabbelt <palmerdabbelt at google.com>

> Signed-off-by: liush <liush at allwinnertech.com>

IIUC you're supposed to use an actual name.

> ---
>  arch/riscv/mm/fault.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 716d64e..3e560ec13 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -198,6 +198,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  		pmd_t *pmd, *pmd_k;
>  		pte_t *pte_k;
>  		int index;
> +		unsigned long pfn;
>
>  		/* User mode accesses just cause a SIGSEGV */
>  		if (user_mode(regs))
> @@ -212,7 +213,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  		 * of a task switch.
>  		 */
>  		index = pgd_index(addr);
> -		pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
> +		pfn = csr_read(CSR_SATP) & SATP_PPN;
> +		pgd = (pgd_t *)pfn_to_virt(pfn) + index;
>  		pgd_k = init_mm.pgd + index;
>
>  		if (!pgd_present(*pgd_k))