Re: [XEN PATCH v2 01/15] x86: introduce AMD-V and Intel VT-x Kconfig options

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.05.2024 10:59, Sergiy Kibrik wrote:
> From: Xenia Ragiadakou <burzalodowa@xxxxxxxxx>
> 
> Introduce two new Kconfig options, SVM and VMX, to allow code
> specific to each virtualization technology to be separated and, when not
> required, stripped.
> CONFIG_SVM will be used to enable virtual machine extensions on platforms that
> implement the AMD Virtualization Technology (AMD-V).
> CONFIG_VMX will be used to enable virtual machine extensions on platforms that
> implement the Intel Virtualization Technology (Intel VT-x).
> 
> Both features depend on HVM support.
> 
> Since, at this point, disabling any of them would cause Xen to not compile,
> the options are enabled by default if HVM and are not selectable by the user.
> 
> No functional change intended.
> 
> Signed-off-by: Xenia Ragiadakou <burzalodowa@xxxxxxxxx>
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>

In principle I'm okay with this, so
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Nevertheless, ...

> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -122,6 +122,12 @@ config HVM
>  
>         If unsure, say Y.
>  
> +config SVM
> +     def_bool HVM
> +
> +config VMX
> +     def_bool HVM

... VT-x having a sub-technology abbreviated as SVM (Secure Virtual Memory),
I wonder if we wouldn't be better off using AMD_SVM and INTEL_VMX. Andrew,
Roger?

> --- a/xen/arch/x86/mm/Makefile
> +++ b/xen/arch/x86/mm/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_MEM_SHARING) += mem_sharing.o
>  obj-$(CONFIG_HVM) += nested.o
>  obj-$(CONFIG_HVM) += p2m.o
>  obj-y += p2m-basic.o
> -obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o p2m-pt.o
> +obj-$(CONFIG_VMX) += p2m-ept.o
> +obj-$(CONFIG_HVM) += p2m-pod.o p2m-pt.o
>  obj-y += paging.o
>  obj-y += physmap.o

Just as a remark, with no request for you to change anything right here:
With SVM=n and SHADOW_PAGING=n, I don't think we really need to build
p2m-pt.c. Yet of course this may require adjustments outside of the
Makefile to then actually build correctly.

Jan