Re: [PATCH] x86/vsyscall/64: Use proper accessor to update p4d entry

[Andy Lutomirski]

On Mon, Mar 19, 2018 at 2:31 PM, Boris Ostrovsky
<boris.ostrovsky@xxxxxxxxxx> wrote:
> Writing to it directly does not work for Xen PV guests.

Whoops, my bad.

Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>

>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
>  arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
> index 8560ef68a9d6..317be365bce3 100644
> --- a/arch/x86/entry/vsyscall/vsyscall_64.c
> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c
> @@ -347,7 +347,7 @@ void __init set_vsyscall_pgtable_user_bits(pgd_t *root)
>         set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
>         p4d = p4d_offset(pgd, VSYSCALL_ADDR);
>  #if CONFIG_PGTABLE_LEVELS >= 5
> -       p4d->p4d |= _PAGE_USER;
> +       set_p4d(p4d, __p4d(p4d_val(*p4d) | _PAGE_USER));
>  #endif
>         pud = pud_offset(p4d, VSYSCALL_ADDR);
>         set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));
> --
> 2.14.3
>