From: David Woodhouse <dwmw@amazon.co.uk>

The XEN_EMU option will cover core Xen support in target/, which exists
only for x86 with KVM today but could theoretically also be implemented
on Arm/Aarch64 and with TCG or other accelerators. It will also cover
the support for architecture-independent grant table and event channel
support which will be added in hw/i386/kvm/ (on the basis that the
non-KVM support is very theoretical and making it not use KVM directly
seems like gratuitous overengineering at this point).

The XENFV_MACHINE option is for the xenfv platform support, which will
now be used both by XEN_EMU and by real Xen.

The XEN option remains dependent on the Xen runtime libraries, and covers
support for real Xen. Some code which currently resides under CONFIG_XEN
will be moving to CONFIG_XENFV_MACHINE over time.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 hw/Kconfig      | 1 +
 hw/i386/Kconfig | 5 +++++
 hw/xen/Kconfig  | 3 +++
 meson.build     | 1 +
 4 files changed, 10 insertions(+)
 create mode 100644 hw/xen/Kconfig

diff --git a/hw/Kconfig b/hw/Kconfig
index 38233bbb0f..ba62ff6417 100644
--- a/hw/Kconfig
+++ b/hw/Kconfig
@@ -41,6 +41,7 @@ source tpm/Kconfig
 source usb/Kconfig
 source virtio/Kconfig
 source vfio/Kconfig
+source xen/Kconfig
 source watchdog/Kconfig
 
 # arch Kconfig
diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
index d22ac4a4b9..c9fd577997 100644
--- a/hw/i386/Kconfig
+++ b/hw/i386/Kconfig
@@ -137,3 +137,8 @@ config VMPORT
 config VMMOUSE
     bool
     depends on VMPORT
+
+config XEN_EMU
+    bool
+    default y
+    depends on KVM && (I386 || X86_64)
diff --git a/hw/xen/Kconfig b/hw/xen/Kconfig
new file mode 100644
index 0000000000..755c8b1faf
--- /dev/null
+++ b/hw/xen/Kconfig
@@ -0,0 +1,3 @@
+config XENFV_MACHINE
+    bool
+    default y if (XEN || XEN_EMU)
diff --git a/meson.build b/meson.build
index 5c6b5a1c75..9348cf572c 100644
--- a/meson.build
+++ b/meson.build
@@ -3828,6 +3828,7 @@ if have_system
   if xen.found()
     summary_info += {'xen ctrl version':  xen.version()}
   endif
+  summary_info += {'Xen emulation':     config_all.has_key('CONFIG_XEN_EMU')}
 endif
 summary_info += {'TCG support':       config_all.has_key('CONFIG_TCG')}
 if config_all.has_key('CONFIG_TCG')
-- 
2.35.3

On 16/12/2022 00:40, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> The XEN_EMU option will cover core Xen support in target/, which exists
> only for x86 with KVM today but could theoretically also be implemented
> on Arm/Aarch64 and with TCG or other accelerators. It will also cover
> the support for architecture-independent grant table and event channel
> support which will be added in hw/i386/kvm/ (on the basis that the
> non-KVM support is very theoretical and making it not use KVM directly
> seems like gratuitous overengineering at this point).
> 
> The XENFV_MACHINE option is for the xenfv platform support, which will
> now be used both by XEN_EMU and by real Xen.
> 
> The XEN option remains dependent on the Xen runtime libraries, and covers
> support for real Xen. Some code which currently resides under CONFIG_XEN
> will be moving to CONFIG_XENFV_MACHINE over time.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   hw/Kconfig      | 1 +
>   hw/i386/Kconfig | 5 +++++
>   hw/xen/Kconfig  | 3 +++
>   meson.build     | 1 +
>   4 files changed, 10 insertions(+)
>   create mode 100644 hw/xen/Kconfig
> 

Reviewed-by: Paul Durrant <paul@xen.org>