Re: [PATCH V4 09/10] xen/arm: check "xen,static-mem" property during domain construction

[Julien Grall <julien@xen.org>]

Hi,

On 28/07/2021 11:27, Penny Zheng wrote:
> This commit checks "xen,static-mem" device tree property in /domUx node,
> to determine whether domain is on Static Allocation, when constructing
> domain during boot-up.
> 
> Right now, the implementation of allocate_static_memory is missing, and
> will be introduced later. It just BUG() out at the moment.

I think the code is small enough to fold it in patch #10. In fact...

> 
> Signed-off-by: Penny Zheng <penny.zheng@arm.com>
> ---
>   xen/arch/arm/domain_build.c | 37 ++++++++++++++++++++++++++++++++++++-
>   1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 6c86d52781..cdb16f2086 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2425,6 +2425,37 @@ static int __init construct_domU(struct domain *d,
>       struct kernel_info kinfo = {};
>       int rc;
>       u64 mem;
> +    const struct dt_property *static_mem_prop;
> +    u32 static_mem_addr_cells, static_mem_size_cells;
> +    bool static_mem = false;

You don't need those information outside of allocate_static_memory(). So 
I think it would be best to move the code in that function.

> +
> +    /*
> +     * Guest RAM could be static memory which will be specified through
> +     * "xen,static-mem" property.
> +     */
> +    static_mem_prop = dt_find_property(node, "xen,static-mem", NULL);
> +    if ( static_mem_prop )
> +    {
> +        static_mem = true;
> +
> +        if ( !dt_property_read_u32(node, "#xen,static-mem-address-cells",
> +                                   &static_mem_addr_cells) )
> +        {
> +            printk("Error building DomU: cannot read "
> +                   "\"#xen,static-mem-address-cells\" property\n");
We don't split comment over multi-line (even they are more than 80 
characters). This is to help grep message in the code.

Although for this one I would replaced "Error building Domu:" with 
simply with the domain ID (you can use %pd and 'd'). The caller will 
then print there was an error during building.


> +            return -EINVAL;
> +        }
> +
> +        if ( !dt_property_read_u32(node, "#xen,static-mem-size-cells",
> +                                   &static_mem_size_cells) )
> +        {
> +            printk("Error building DomU: cannot read "
> +                   "\"#xen,static-mem-size-cells\" property\n");

My remark applies here as well.

> +            return -EINVAL;
> +        }
> +
> +        BUG_ON(static_mem_size_cells > 2 || static_mem_addr_cells > 2);

Did we validate the DT before hand? If not, then I think

> +    }


>   
>       rc = dt_property_read_u64(node, "memory", &mem);
>       if ( !rc )
> @@ -2452,7 +2483,11 @@ static int __init construct_domU(struct domain *d,
>       /* type must be set before allocate memory */
>       d->arch.type = kinfo.type;
>   #endif
> -    allocate_memory(d, &kinfo);
> +    if ( !static_mem )

With my suggestion above, the check can be replaced with:

if ( !dt_find_property(node, "xen,static-mem", NULL) )

> +        allocate_memory(d, &kinfo);
> +    else
> +        /* TODO: allocate_static_memory(...). */
> +        BUG();
>   
>       rc = prepare_dtb_domU(d, &kinfo);
>       if ( rc < 0 )
> 

Cheers,

-- 
Julien Grall