Re: [XEN][RFC PATCH v4 12/16] xen/arm: Implement device tree node removal functionalities

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.12.2022 07:18, Vikram Garhwal wrote:
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -1079,6 +1079,23 @@ typedef struct xen_sysctl_cpu_policy 
> xen_sysctl_cpu_policy_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cpu_policy_t);
>  #endif
>  
> +#define XEN_SYSCTL_DT_OVERLAY_ADD                   1
> +#define XEN_SYSCTL_DT_OVERLAY_REMOVE                2
> +
> +/*
> + * XEN_SYSCTL_dt_overlay
> + * Performs addition/removal of device tree nodes under parent node using 
> dtbo.
> + * This does in three steps:
> + *  - Adds/Removes the nodes from dt_host.
> + *  - Adds/Removes IRQ permission for the nodes.
> + *  - Adds/Removes MMIO accesses.
> + */
> +struct xen_sysctl_dt_overlay {
> +    XEN_GUEST_HANDLE_64(void) overlay_fdt;
> +    uint32_t overlay_fdt_size;  /* Overlay dtb size. */
> +    uint8_t overlay_op; /* Add or remove. */
> +};
> +
>  struct xen_sysctl {
>      uint32_t cmd;
>  #define XEN_SYSCTL_readconsole                    1
> @@ -1109,6 +1126,7 @@ struct xen_sysctl {
>  #define XEN_SYSCTL_livepatch_op                  27
>  /* #define XEN_SYSCTL_set_parameter              28 */
>  #define XEN_SYSCTL_get_cpu_policy                29
> +#define XEN_SYSCTL_dt_overlay                    30
>      uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
>      union {
>          struct xen_sysctl_readconsole       readconsole;
> @@ -1139,6 +1157,7 @@ struct xen_sysctl {
>  #if defined(__i386__) || defined(__x86_64__)
>          struct xen_sysctl_cpu_policy        cpu_policy;
>  #endif
> +        struct xen_sysctl_dt_overlay        dt_overlay;

For now your additions are Arm-only, aren't they? You want to use
#ifdef-ary similar to what you see in context in this last hunk then,
to avoid undue exposure.

Jan