Re: [PATCH v4 08/11] xen/arm: use colored allocator for p2m page tables

[Julien Grall <julien@xxxxxxx>]

Hi Carlo,

On 23/01/2023 15:47, Carlo Nonato wrote:
> Cache colored domains can benefit from having p2m page tables allocated
> with the same coloring schema so that isolation can be achieved also for
> those kind of memory accesses.
> In order to do that, the domain struct is passed to the allocator and the
> MEMF_no_owner flag is used.
>
> Signed-off-by: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
> Signed-off-by: Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>
> ---
> v4:
> - fixed p2m page allocation using MEMF_no_owner memflag
> ---
>   xen/arch/arm/p2m.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 948f199d84..f9faeb61af 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -4,6 +4,7 @@
>   #include <xen/iocap.h>
>   #include <xen/ioreq.h>
>   #include <xen/lib.h>
> +#include <xen/llc_coloring.h>
>   #include <xen/sched.h>
>   #include <xen/softirq.h>
>   
> @@ -56,7 +57,10 @@ static struct page_info *p2m_alloc_page(struct domain *d)
>        */
>       if ( is_hardware_domain(d) )
>       {
> -        pg = alloc_domheap_page(NULL, 0);
> +        if ( is_domain_llc_colored(d) )
> +            pg = alloc_domheap_page(d, MEMF_no_owner);
> +        else
> +            pg = alloc_domheap_page(NULL, 0);
I don't think we need to special case a colored domain here.You could 
simply always pass the domain/MEMF_no_owner and let the function decide 
what to do.
This approach would also be useful when NUMA will be supported on Arm 
(the series is still under review).
>           if ( pg == NULL )
>               printk(XENLOG_G_ERR "Failed to allocate P2M pages for hwdom.\n");
>       }
> @@ -105,7 +109,10 @@ int p2m_set_allocation(struct domain *d, unsigned long 
> pages, bool *preempted)
>           if ( d->arch.paging.p2m_total_pages < pages )
>           {
>               /* Need to allocate more memory from domheap */
> -            pg = alloc_domheap_page(NULL, 0);
> +            if ( is_domain_llc_colored(d) )
> +                pg = alloc_domheap_page(d, MEMF_no_owner);
> +            else
> +                pg = alloc_domheap_page(NULL, 0);
Ditto.

>               if ( pg == NULL )
>               {
>                   printk(XENLOG_ERR "Failed to allocate P2M pages.\n");
Cheers,

--
Julien Grall