Re: [PATCH v2 7/8] xen/common: dom0less: introduce common domain-build.c

[Jan Beulich <jbeulich@suse.com>]

On 14.04.2025 17:56, Oleksii Kurochko wrote:
> --- a/xen/include/xen/fdt-domain-build.h
> +++ b/xen/include/xen/fdt-domain-build.h
> @@ -5,6 +5,7 @@
>  #include <xen/bootfdt.h>
>  #include <xen/device_tree.h>
>  #include <xen/fdt-kernel.h>
> +#include <xen/mm.h>
>  #include <xen/types.h>
>  
>  #if __has_include(<asm/domain_build.h>)
> @@ -32,7 +33,37 @@ int make_memory_node(const struct kernel_info *kinfo, int addrcells,
>                       int sizecells, const struct membanks *mem);
>  int make_timer_node(const struct kernel_info *kinfo);
>  
> -unsigned int get_allocation_size(paddr_t size);
> +
> +static inline int get_allocation_size(paddr_t size)
> +{
> +    /*
> +     * get_order_from_bytes returns the order greater than or equal to
> +     * the given size, but we need less than or equal. Adding one to
> +     * the size pushes an evenly aligned size into the next order, so
> +     * we can then unconditionally subtract 1 from the order which is
> +     * returned.
> +     */
> +    return get_order_from_bytes(size + 1) - 1;
> +}
> +
> +typedef unsigned long (*copy_to_guest_phys_cb)(struct domain *d,
> +                                               paddr_t gpa,
> +                                               void *buf,

This very much looks like the latest now, when the code is made common,
it wants to be const void *. Even if this may require another prereq
patch.

However, instead of using a function pointer, couldn't the now common
code call copy_to_guest_phys_flush_dcache() conditionally upon
IS_ENABLED(CONFIG_<whatever>)? Or provide a weak
copy_to_guest_phys_flush_dcache() which would simply call
copy_to_guest_phys()?

Jan