Re: [PATCH v3 03/19] xen/arm: p2m: Replace level_{orders, masks} arrays with XEN_PT_LEVEL_{ORDER, MASK}

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Julien,

> On 21 Feb 2022, at 10:22, Julien Grall <julien@xxxxxxx> wrote:
> 
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> The array level_orders and level_masks can be replaced with the
> recently introduced macros LEVEL_ORDER and LEVEL_MASK.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

One open question: At this stage the convenience aliases that you
kept in include/asm/lpae.h are used in a very limited number of places.
Could we remove those and use only XEN_PT_LEVEL_* to make the
code a bit more coherent.

Not something to do here but could be done in a following patch after
this serie

Cheers
Bertrand

> 
> ---
>    Changes in v3:
>        - Fix clashes after prefixing the PT macros with XEN_PT_
> 
>    Changes in v2:
>        - New patch
> 
>    The goal is to remove completely the static arrays so they
>    don't need to be global (or duplicated) when adding superpage
>    support for Xen PT.
> 
>    This also has the added benefits to replace a couple of loads
>    with only a few instructions working on immediate.
> ---
> xen/arch/arm/p2m.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 493a1e25879a..1d1059f7d2bd 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -37,12 +37,6 @@ static unsigned int __read_mostly max_vmid = 
> MAX_VMID_8_BIT;
>  */
> unsigned int __read_mostly p2m_ipa_bits = 64;
> 
> -/* Helpers to lookup the properties of each level */
> -static const paddr_t level_masks[] =
> -    { ZEROETH_MASK, FIRST_MASK, SECOND_MASK, THIRD_MASK };
> -static const uint8_t level_orders[] =
> -    { ZEROETH_ORDER, FIRST_ORDER, SECOND_ORDER, THIRD_ORDER };
> -
> static mfn_t __read_mostly empty_root_mfn;
> 
> static uint64_t generate_vttbr(uint16_t vmid, mfn_t root_mfn)
> @@ -233,7 +227,7 @@ static lpae_t *p2m_get_root_pointer(struct p2m_domain 
> *p2m,
>      * we can't use (P2M_ROOT_LEVEL - 1) because the root level might be
>      * 0. Yet we still want to check if all the unused bits are zeroed.
>      */
> -    root_table = gfn_x(gfn) >> (level_orders[P2M_ROOT_LEVEL] +
> +    root_table = gfn_x(gfn) >> (XEN_PT_LEVEL_ORDER(P2M_ROOT_LEVEL) +
>                                 XEN_PT_LPAE_SHIFT);
>     if ( root_table >= P2M_ROOT_PAGES )
>         return NULL;
> @@ -380,7 +374,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
>     if ( gfn_x(gfn) > gfn_x(p2m->max_mapped_gfn) )
>     {
>         for ( level = P2M_ROOT_LEVEL; level < 3; level++ )
> -            if ( (gfn_x(gfn) & (level_masks[level] >> PAGE_SHIFT)) >
> +            if ( (gfn_x(gfn) & (XEN_PT_LEVEL_MASK(level) >> PAGE_SHIFT)) >
>                  gfn_x(p2m->max_mapped_gfn) )
>                 break;
> 
> @@ -423,7 +417,8 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
>          * The entry may point to a superpage. Find the MFN associated
>          * to the GFN.
>          */
> -        mfn = mfn_add(mfn, gfn_x(gfn) & ((1UL << level_orders[level]) - 1));
> +        mfn = mfn_add(mfn,
> +                      gfn_x(gfn) & ((1UL << XEN_PT_LEVEL_ORDER(level)) - 1));
> 
>         if ( valid )
>             *valid = lpae_is_valid(entry);
> @@ -434,7 +429,7 @@ out_unmap:
> 
> out:
>     if ( page_order )
> -        *page_order = level_orders[level];
> +        *page_order = XEN_PT_LEVEL_ORDER(level);
> 
>     return mfn;
> }
> @@ -808,7 +803,7 @@ static bool p2m_split_superpage(struct p2m_domain *p2m, 
> lpae_t *entry,
>     /* Convenience aliases */
>     mfn_t mfn = lpae_get_mfn(*entry);
>     unsigned int next_level = level + 1;
> -    unsigned int level_order = level_orders[next_level];
> +    unsigned int level_order = XEN_PT_LEVEL_ORDER(next_level);
> 
>     /*
>      * This should only be called with target != level and the entry is
> -- 
> 2.32.0
>