Re: [RFC PATCH] xen/arm: p2m don't fall over on FEAT_LPA enabled hw

[Julien Grall <julien@xxxxxxx>]

Hi Alex,

On 26/04/2022 17:05, Alex Bennée wrote:
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index fb71fa4c1c..e5a88095f8 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -2030,7 +2030,7 @@ void __init setup_virt_paging(void)
>           unsigned int root_order; /* Page order of the root of the p2m */
>           unsigned int sl0;    /* Desired SL0, maximum in comment */
>       } pa_range_info[] = {
> -        /* T0SZ minimum and SL0 maximum from ARM DDI 0487A.b Table D4-5 */
> +        /* T0SZ minimum and SL0 maximum from ARM DDI 0487H.a Table D5-6 */
>           /*      PA size, t0sz(min), root-order, sl0(max) */
>           [0] = { 32,      32/*32*/,  0,          1 },
>           [1] = { 36,      28/*28*/,  0,          1 },
> @@ -2038,7 +2038,7 @@ void __init setup_virt_paging(void)
>           [3] = { 42,      22/*22*/,  3,          1 },
>           [4] = { 44,      20/*20*/,  0,          2 },
>           [5] = { 48,      16/*16*/,  0,          2 },
> -        [6] = { 0 }, /* Invalid */
> +        [6] = { 52,      12/*12*/,  3,          3 },
>           [7] = { 0 }  /* Invalid */
>       };
>   
> @@ -2069,10 +2069,13 @@ void __init setup_virt_paging(void)
>           }
>       }
>   
> -    /* pa_range is 4 bits, but the defined encodings are only 3 bits */
> +    /* pa_range is 4 bits but we don't support all modes */
>       if ( pa_range >= ARRAY_SIZE(pa_range_info) || 
> !pa_range_info[pa_range].pabits )
>           panic("Unknown encoding of ID_AA64MMFR0_EL1.PARange %x\n", pa_range);
>   
> +    if ( pa_range > 5 )
> +        pa_range = 5;
I think it would be better to restrict the p2m_ipa_bits rather than the 
PA range. This can be done by initializing p2m_ipa_bits to PADDR_BITS (48).
Cheers,

--
Julien Grall