Re: [PATCH v3] xen/arm: don't assign domU static-mem to dom0 as reserved-memory

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 10/11/2021 20:18, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
>
> DomUs static-mem ranges are added to the reserved_mem array for
> accounting, but they shouldn't be assigned to dom0 as the other regular
> reserved-memory ranges in device tree.
>
> In make_memory_nodes, fix the error by skipping banks with xen_domain
> set to true in the reserved-memory array. Also make sure to use the
> first valid (!xen_domain) start address for the memory node name.
>
> Fixes: 41c031ff437b ("xen/arm: introduce domain on Static Allocation")
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

> ---
> Changes in v3:
> - move BUG_ON inside the loop
>
> Changes in v2:
> - improve commit message
> - improve in-code comment
> - update nr_cells appropriately
> ---
>   xen/arch/arm/domain_build.c | 23 +++++++++++++++++------
>   1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 9e92b640cd..dafbc13962 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -862,21 +862,25 @@ static int __init make_memory_node(const struct domain *d,
>   {
>       int res, i;
>       int reg_size = addrcells + sizecells;
> -    int nr_cells = reg_size * mem->nr_banks;
> +    int nr_cells = 0;
>       /* Placeholder for memory@ + a 64-bit number + \0 */
>       char buf[24];
>       __be32 reg[NR_MEM_BANKS * 4 /* Worst case addrcells + sizecells */];
>       __be32 *cells;
>   
> -    BUG_ON(nr_cells >= ARRAY_SIZE(reg));
>       if ( mem->nr_banks == 0 )
>           return -ENOENT;
>   
> -    dt_dprintk("Create memory node (reg size %d, nr cells %d)\n",
> -               reg_size, nr_cells);
> +    /* find first memory range not bound to a Xen domain */
> +    for ( i = 0; i < mem->nr_banks && mem->bank[i].xen_domain; i++ )
> +        ;
> +    if ( i == mem->nr_banks )
> +        return 0;
> +
> +    dt_dprintk("Create memory node\n");
>   
>       /* ePAPR 3.4 */
> -    snprintf(buf, sizeof(buf), "memory@%"PRIx64, mem->bank[0].start);
> +    snprintf(buf, sizeof(buf), "memory@%"PRIx64, mem->bank[i].start);
>       res = fdt_begin_node(fdt, buf);
>       if ( res )
>           return res;
> @@ -886,17 +890,24 @@ static int __init make_memory_node(const struct domain *d,
>           return res;
>   
>       cells = &reg[0];
> -    for ( i = 0 ; i < mem->nr_banks; i++ )
> +    for ( ; i < mem->nr_banks; i++ )
>       {
>           u64 start = mem->bank[i].start;
>           u64 size = mem->bank[i].size;
>   
> +        if ( mem->bank[i].xen_domain )
> +            continue;
> +
>           dt_dprintk("  Bank %d: %#"PRIx64"->%#"PRIx64"\n",
>                      i, start, start + size);
>   
> +        nr_cells += reg_size;
> +        BUG_ON(nr_cells >= ARRAY_SIZE(reg));
>           dt_child_set_range(&cells, addrcells, sizecells, start, size);
>       }
>   
> +    dt_dprintk("(reg size %d, nr cells %d)\n", reg_size, nr_cells);
> +
>       res = fdt_property(fdt, "reg", reg, nr_cells * sizeof(*reg));
>       if ( res )
>           return res;
--
Julien Grall