RE: [PATCH v1 01/18] kconfig: allow configuration of maximum modules

[Henry Wang <Henry.Wang@xxxxxxx>]

Hi Daniel,

> -----Original Message-----
> Subject: [PATCH v1 01/18] kconfig: allow configuration of maximum modules
> 
> For x86 the number of allowable multiboot modules varies between the
> different
> entry points, non-efi boot, pvh boot, and efi boot. In the case of both Arm
> and
> x86 this value is fixed to values based on generalized assumptions. With
> hyperlaunch for x86 and dom0less on Arm, use of static sizes results in large
> allocations compiled into the hypervisor that will go unused by many use
> cases.
> 
> This commit introduces a Kconfig variable that is set with sane defaults based
> on configuration selection. This variable is in turned used as the array size
> for the cases where a static allocated array of boot modules is declared.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Christopher Clark <christopher.clark@xxxxxxxxxx>

Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>

> ---
>  xen/arch/Kconfig                  | 12 ++++++++++++
>  xen/arch/arm/include/asm/setup.h  |  5 +++--
>  xen/arch/x86/efi/efi-boot.h       |  2 +-
>  xen/arch/x86/guest/xen/pvh-boot.c |  2 +-
>  xen/arch/x86/setup.c              |  4 ++--
>  5 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig
> index f16eb0df43..24139057be 100644
> --- a/xen/arch/Kconfig
> +++ b/xen/arch/Kconfig
> @@ -17,3 +17,15 @@ config NR_CPUS
>         For CPU cores which support Simultaneous Multi-Threading or
> similar
>         technologies, this the number of logical threads which Xen will
>         support.
> +
> +config NR_BOOTMODS
> +     int "Maximum number of boot modules that a loader can pass"
> +     range 1 32768
> +     default "8" if X86
> +     default "32" if ARM
> +     help
> +       Controls the build-time size of various arrays allocated for
> +       parsing the boot modules passed by a loader when starting Xen.
> +
> +       This is of particular interest when using Xen's hypervisor domain
> +       capabilities such as dom0less.
> diff --git a/xen/arch/arm/include/asm/setup.h
> b/xen/arch/arm/include/asm/setup.h
> index 2bb01ecfa8..312a3e4209 100644
> --- a/xen/arch/arm/include/asm/setup.h
> +++ b/xen/arch/arm/include/asm/setup.h
> @@ -10,7 +10,8 @@
> 
>  #define NR_MEM_BANKS 256
> 
> -#define MAX_MODULES 32 /* Current maximum useful modules */
> +/* Current maximum useful modules */
> +#define MAX_MODULES CONFIG_NR_BOOTMODS
> 
>  typedef enum {
>      BOOTMOD_XEN,
> @@ -38,7 +39,7 @@ struct meminfo {
>   * The domU flag is set for kernels and ramdisks of "xen,domain" nodes.
>   * The purpose of the domU flag is to avoid getting confused in
>   * kernel_probe, where we try to guess which is the dom0 kernel and
> - * initrd to be compatible with all versions of the multiboot spec.
> + * initrd to be compatible with all versions of the multiboot spec.

Thanks for taking the chance to remove the space in the end of the sentence.

Kind regards,
Henry