Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 14/19] xen/arm32: mm: Avoid cleaning the cache for secondary CPUs page-tables

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 14 May 2019, Julien Grall wrote:
> The page-table walker is configured to use the same shareability and
> cacheability as the access performed when updating the page-tables. This
> means cleaning the cache for secondary CPUs runtime page-tables is
> unnecessary.

All right. Is there an explicit configuration for the shareability and
cacheability used by the page-table walker or is it specified as such in
the Arm Arm? Also, isn't it possible that CPUs on a different cluster
(big.LITTLE) would have issues with this if the cache could be split
between the two clusters?


> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
> 
> ---
>     Changes in v2:
>         - Add Andrii's reviewed-by
> ---
>  xen/arch/arm/mm.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index cda2847d00..6db7dda0da 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -769,9 +769,6 @@ int init_secondary_pagetables(int cpu)
>          
> write_pte(&first[first_table_offset(DOMHEAP_VIRT_START+i*FIRST_SIZE)], pte);
>      }
>  
> -    clean_dcache_va_range(first, PAGE_SIZE);
> -    clean_dcache_va_range(domheap, DOMHEAP_SECOND_PAGES*PAGE_SIZE);
> -
>      per_cpu(xen_pgtable, cpu) = first;
>      per_cpu(xen_dommap, cpu) = domheap;
>  
> -- 
> 2.11.0
> 

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