Re: [PATCH v2 2/2] x86/Kconfig: Introduce CONFIG_{AMD,INTEL} and conditionalise ucode

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.10.2023 22:55, Andrew Cooper wrote:
> We eventually want to be able to build a stripped down Xen for a single
> platform.  Make a start with CONFIG_{AMD,INTEL} (hidden behind EXPERT, but
> available to randconfig), and adjust the microcode logic.
> 
> No practical change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
> CC: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> CC: Xenia Ragiadakou <xenia.ragiadakou@xxxxxxx>
> 
> I've intentionally ignored the other vendors for now.  They can be put into
> Kconfig by whomever figures out the actual dependencies between their init
> routines.
> 
> v2:
>  * Tweak text

What about the indentation issues mentioned in reply to v1?

As to using un-amended AMD and INTEL - Roger, what's your view here?
I'm not outright opposed, but to me it feels misleading to omit CPU
from those Kconfig symbols.

Jan

> ---
>  xen/arch/x86/Kconfig                 |  2 ++
>  xen/arch/x86/Kconfig.cpu             | 22 ++++++++++++++++++++++
>  xen/arch/x86/cpu/microcode/Makefile  |  4 ++--
>  xen/arch/x86/cpu/microcode/private.h |  9 +++++++++
>  4 files changed, 35 insertions(+), 2 deletions(-)
>  create mode 100644 xen/arch/x86/Kconfig.cpu
> 
> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
> index eac77573bd75..d9eacdd7e0fa 100644
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -49,6 +49,8 @@ config HAS_CC_CET_IBT
>  
>  menu "Architecture Features"
>  
> +source "arch/x86/Kconfig.cpu"
> +
>  source "arch/Kconfig"
>  
>  config PV
> diff --git a/xen/arch/x86/Kconfig.cpu b/xen/arch/x86/Kconfig.cpu
> new file mode 100644
> index 000000000000..3c5d88fdfd16
> --- /dev/null
> +++ b/xen/arch/x86/Kconfig.cpu
> @@ -0,0 +1,22 @@
> +menu "Supported CPU vendors"
> +     visible if EXPERT
> +
> +config AMD
> +     bool "AMD"
> +        default y
> +        help
> +          Detection, tunings and quirks for AMD platforms.
> +
> +       May be turned off in builds targetting other vendors.  Otherwise,
> +       must be enabled for Xen to work suitably on AMD platforms.
> +
> +config INTEL
> +     bool "Intel"
> +        default y
> +        help
> +          Detection, tunings and quirks for Intel platforms.
> +
> +       May be turned off in builds targetting other vendors.  Otherwise,
> +       must be enabled for Xen to work suitably on Intel platforms.
> +
> +endmenu
> diff --git a/xen/arch/x86/cpu/microcode/Makefile 
> b/xen/arch/x86/cpu/microcode/Makefile
> index aae235245b06..30d600544f45 100644
> --- a/xen/arch/x86/cpu/microcode/Makefile
> +++ b/xen/arch/x86/cpu/microcode/Makefile
> @@ -1,3 +1,3 @@
> -obj-y += amd.o
> +obj-$(CONFIG_AMD) += amd.o
>  obj-y += core.o
> -obj-y += intel.o
> +obj-$(CONFIG_INTEL) += intel.o
> diff --git a/xen/arch/x86/cpu/microcode/private.h 
> b/xen/arch/x86/cpu/microcode/private.h
> index b58611e908aa..da556fe5060a 100644
> --- a/xen/arch/x86/cpu/microcode/private.h
> +++ b/xen/arch/x86/cpu/microcode/private.h
> @@ -70,7 +70,16 @@ struct microcode_ops {
>   * support available) and (not) ops->apply_microcode (i.e. read only).
>   * Otherwise, all hooks must be filled in.
>   */
> +#ifdef CONFIG_AMD
>  void ucode_probe_amd(struct microcode_ops *ops);
> +#else
> +static inline void ucode_probe_amd(struct microcode_ops *ops) {}
> +#endif
> +
> +#ifdef CONFIG_INTEL
>  void ucode_probe_intel(struct microcode_ops *ops);
> +#else
> +static inline void ucode_probe_intel(struct microcode_ops *ops) {}
> +#endif
>  
>  #endif /* ASM_X86_MICROCODE_PRIVATE_H */