Re: [XEN v4 09/11] xen/arm: Restrict zeroeth_table_offset for ARM_64

[Julien Grall <julien@xxxxxxx>]

Hi,

On 21/03/2023 14:03, Ayan Kumar Halder wrote:
> When 32 bit physical addresses are used (ie ARM_PA_32=y),
> "va >> ZEROETH_SHIFT" causes an overflow.
> Also, there is no zeroeth level page table on Arm 32-bit.
>
> Also took the opportunity to clean up dump_pt_walk(). One could use
> DECLARE_OFFSETS() macro instead of declaring the declaring an array
> of page table offsets.
>
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
This should be re-ordered so the signed-off-by tag is first.

> ---
> Changes from -
>
> v1 - Removed the duplicate declaration for DECLARE_OFFSETS.
>
> v2 - 1. Reworded the commit message.
> 2. Use CONFIG_ARM_PA_32 to restrict zeroeth_table_offset.
>
> v3 - 1. Added R-b and Ack.
>
>   xen/arch/arm/include/asm/lpae.h | 4 ++++
>   xen/arch/arm/mm.c               | 7 +------
>   2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/lpae.h b/xen/arch/arm/include/asm/lpae.h
> index 3fdd5d0de2..0d40388f93 100644
> --- a/xen/arch/arm/include/asm/lpae.h
> +++ b/xen/arch/arm/include/asm/lpae.h
> @@ -259,7 +259,11 @@ lpae_t mfn_to_xen_entry(mfn_t mfn, unsigned int attr);
>   #define first_table_offset(va)  TABLE_OFFSET(first_linear_offset(va))
>   #define second_table_offset(va) TABLE_OFFSET(second_linear_offset(va))
>   #define third_table_offset(va)  TABLE_OFFSET(third_linear_offset(va))
> +#ifdef CONFIG_ARM_PA_BITS_32
I know I already acked this patch. However, looking at the previous 
patch, you are using CONFIG_PHYS_ADDR_T_32 but here you are using 
CONFIG_ARM_PA_BITS_32.
It is not fully clear to me why you differ in the #ifdef approach. Can 
you clarify?
> +#define zeroeth_table_offset(va)  0
> +#else
>   #define zeroeth_table_offset(va)  TABLE_OFFSET(zeroeth_linear_offset(va))
> +#endif
>   
>   /*
>    * Macros to define page-tables:
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index d8b43ef38c..41e0896b0f 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -221,12 +221,7 @@ void dump_pt_walk(paddr_t ttbr, paddr_t addr,
>   {
>       static const char *level_strs[4] = { "0TH", "1ST", "2ND", "3RD" };
>       const mfn_t root_mfn = maddr_to_mfn(ttbr);
> -    const unsigned int offsets[4] = {
> -        zeroeth_table_offset(addr),
> -        first_table_offset(addr),
> -        second_table_offset(addr),
> -        third_table_offset(addr)
> -    };
> +    DECLARE_OFFSETS(offsets, addr);
>       lpae_t pte, *mapping;
>       unsigned int level, root_table;
>   
Cheers,

--
Julien Grall