Re: [PATCH v3 13/18] xen/arm: mm: Allow xen_pt_update() to work with the current root table

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 12 Dec 2022, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> At the moment, xen_pt_update() will only work on the runtime page tables.
> In follow-up patches, we will also want to use the helper to update
> the boot page tables.
> 
> All the existing callers of xen_pt_update() expects to modify the
> current page-tables. Therefore, we can read the root physical address
> directly from TTBR0_EL2.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

> ---
> 
>     Changes in v2:
>         - Patch added
> ---
>  xen/arch/arm/mm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index cc11f5c639e6..26d6b70410c5 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -1114,7 +1114,7 @@ static int xen_pt_update(unsigned long virt,
>       *
>       * XXX: Add a check.
>       */
> -    const mfn_t root = virt_to_mfn(THIS_CPU_PGTABLE);
> +    const mfn_t root = maddr_to_mfn(READ_SYSREG64(TTBR0_EL2));
>  
>      /*
>       * The hardware was configured to forbid mapping both writeable and
> -- 
> 2.38.1
>