From: Xenia Ragiadakou <burzalodowa@gmail.com>

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@gmail.com>
Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
CC: Jan Beulich <jbeulich@suse.com>
---
changes in v2:
 - simplify kconfig expression to def_bool HVM
 - keep file list in Makefile in alphabetical order
changes in v1:
 - change kconfig option name AMD_SVM/INTEL_VMX -> SVM/VMX
---
 xen/arch/x86/Kconfig         | 6 ++++++
 xen/arch/x86/hvm/Makefile    | 4 ++--
 xen/arch/x86/mm/Makefile     | 3 ++-
 xen/arch/x86/mm/hap/Makefile | 2 +-
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 7e03e4bc55..8c9f8431f0 100644
--- 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
+
 config XEN_SHSTK
 	bool "Supervisor Shadow Stacks"
 	depends on HAS_AS_CET_SS
diff --git a/xen/arch/x86/hvm/Makefile b/xen/arch/x86/hvm/Makefile
index 3464191544..8434badc64 100644
--- a/xen/arch/x86/hvm/Makefile
+++ b/xen/arch/x86/hvm/Makefile
@@ -1,5 +1,5 @@
-obj-y += svm/
-obj-y += vmx/
+obj-$(CONFIG_SVM) += svm/
+obj-$(CONFIG_VMX) += vmx/
 obj-y += viridian/
 
 obj-y += asid.o
diff --git a/xen/arch/x86/mm/Makefile b/xen/arch/x86/mm/Makefile
index 0803ac9297..0128ca7ab6 100644
--- 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
diff --git a/xen/arch/x86/mm/hap/Makefile b/xen/arch/x86/mm/hap/Makefile
index 8ef54b1faa..98c8a87819 100644
--- a/xen/arch/x86/mm/hap/Makefile
+++ b/xen/arch/x86/mm/hap/Makefile
@@ -3,4 +3,4 @@ obj-y += guest_walk_2.o
 obj-y += guest_walk_3.o
 obj-y += guest_walk_4.o
 obj-y += nested_hap.o
-obj-y += nested_ept.o
+obj-$(CONFIG_VMX) += nested_ept.o
-- 
2.25.1

On 15.05.2024 10:59, Sergiy Kibrik wrote:
> From: Xenia Ragiadakou <burzalodowa@gmail.com>
> 
> 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@gmail.com>
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>

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