Re: [PATCH v1 14/14] xen/arm: Add linux,pci-domain property for hwdom if not available.

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 19 Aug 2021, Rahul Singh wrote:
> If the property is not present in the device tree node for host bridge,
> XEN while creating the dtb for hwdom will create this property and
> assigns the already allocated segment to the host bridge
> so that XEN and linux will have the same segment for the host bridges.
> 
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
> ---
>  xen/arch/arm/domain_build.c        | 18 ++++++++++++++++++
>  xen/arch/arm/pci/pci-host-common.c | 21 +++++++++++++++++++++
>  xen/include/asm-arm/pci.h          |  3 +++
>  3 files changed, 42 insertions(+)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 6c86d52781..e0cf2ff19d 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -581,6 +581,24 @@ static int __init write_properties(struct domain *d, 
> struct kernel_info *kinfo,
>              return res;
>      }
>  
> +#ifdef CONFIG_HAS_PCI
> +    if ( dt_device_type_is_equal(node, "pci") )
> +    {
> +        if ( !dt_find_property(node, "linux,pci-domain", NULL) )
> +        {
> +            uint16_t segment;
> +
> +            res = pci_get_host_bridge_segment(node, &segment);
> +            if ( res < 0 )
> +                return res;
> +
> +            res = fdt_property_cell(kinfo->fdt, "linux,pci-domain", segment);
> +            if ( res )
> +                return res;
> +        }
> +    }
> +#endif

If param_pci_enable is false it might be possible that Xen didn't
allocate a segment. In that case, we should just let Linux do whatever
it wants in terms of segment allocation. So I think the code here should
not return error if param_pci_enable is false.
returning an error instead.