Re: [Xen-devel] [PATCH v2] xen/arm64: Fix incorrect memory region size in TCR_EL2

[Julien Grall <julien.grall@xxxxxxx>]

Hi Shanker,

On 14/03/16 16:10, Shanker Donthineni wrote:
> The maximum and minimum values for TxSZ depend on level of
> translation as per AArch64 Virtual Memory System Architecture.
> According to ARM specification DDI0487A_h (sec D4.2.2, page 1752),
> the minimum TxSZ value is 16. If TxSZ is programmed to a value
> smaller than 16 then it is IMPLEMENTATION DEFINED.
>
> This patch sets T0SZ to (64-48)bits since XEN uses all 4 levels
> to cover 48bit (256TB) virtual address instead of value zero.
>
> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>

Regards,

> ---
> Changed since v1:
>      Edit commit descriprtion.
>
>   xen/arch/arm/arm64/head.S | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 19fa2bb..946e2c9 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -342,8 +342,8 @@ skip_bss:
>            * Top byte is used
>            * PT walks use Inner-Shareable accesses,
>            * PT walks are write-back, write-allocate in both cache levels,
> -         * Full 64-bit address space goes through this table. */
> -        ldr   x0, 
> =(TCR_RES1|TCR_SH0_IS|TCR_ORGN0_WBWA|TCR_IRGN0_WBWA|TCR_T0SZ(0))
> +         * 48-bit virtual address space goes through this table. */
> +        ldr   x0, 
> =(TCR_RES1|TCR_SH0_IS|TCR_ORGN0_WBWA|TCR_IRGN0_WBWA|TCR_T0SZ(64-48))
>           /* ID_AA64MMFR0_EL1[3:0] (PARange) corresponds to TCR_EL2[18:16] (PS) 
> */
>           mrs   x1, ID_AA64MMFR0_EL1
>           bfi   x0, x1, #16, #3
--
Julien Grall

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