xen: EXPERT clean-up and introduce UNSUPPORTED

A recent thread [1] has exposed a couple of issues with our current way
of handling EXPERT.

1) It is not obvious that "Configure standard Xen features (expert
users)" is actually the famous EXPERT we keep talking about on xen-devel

2) It is not obvious when we need to enable EXPERT to get a specific
feature

In particular if you want to enable ACPI support so that you can boot
Xen on an ACPI platform, you have to enable EXPERT first. But searching
through the kconfig menu it is really not clear (type '/' and "ACPI"):
nothing in the description tells you that you need to enable EXPERT to
get the option.

So this patch makes things easier by doing two things:

- introduce a new kconfig option UNSUPPORTED which is clearly to enable
  UNSUPPORTED features as defined by SUPPORT.md

- change EXPERT options to UNSUPPORTED where it makes sense: keep
  depending on EXPERT for features made for experts

- tag unsupported features by adding (UNSUPPORTED) to the one-line
  description

- clarify the EXPERT one-line description

[1] https://marc.info/?l=xen-devel&m=160333101228981

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com> [x86,common]
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
CC: andrew.cooper3@citrix.com
CC: george.dunlap@citrix.com
CC: iwj@xenproject.org
CC: jbeulich@suse.com
CC: julien@xen.org
CC: wl@xen.org

diff --git a/xen/Kconfig b/xen/Kconfig
index 34c318bfa2c7bacb0fdf2f459a41e3e2b2808104..bcbd2758e5d37167ce4e4e7ba5d5ea43a04021cc 100644 (file)
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -35,7 +35,7 @@ config DEFCONFIG_LIST
        default ARCH_DEFCONFIG
 
 config EXPERT
-       bool "Configure standard Xen features (expert users)"
+       bool "Configure EXPERT features"
        help
          This option allows certain base Xen options and settings
          to be disabled or tweaked. This is for specialized environments
@@ -45,6 +45,15 @@ config EXPERT
          supported.
        default n
 
+config UNSUPPORTED
+       bool "Configure UNSUPPORTED features"
+       default EXPERT
+       help
+         This option allows certain unsupported Xen options to be changed,
+         which includes non-security-supported, experimental, and tech
+         preview features as defined by SUPPORT.md. (Note that if an option
+         doesn't depend on UNSUPPORTED it doesn't imply that is supported.)
+
 config LTO
        bool "Link Time Optimisation"
        depends on BROKEN

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index c3eb13ea7382a4d9349249e28af4fe3dfec0a6fd..330bbf6232d4b7e5ef511d8783804c3253d08063 100644 (file)
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -32,7 +32,7 @@ menu "Architecture Features"
 source "arch/Kconfig"
 
 config ACPI
-       bool "ACPI (Advanced Configuration and Power Interface) Support" if EXPERT
+       bool "ACPI (Advanced Configuration and Power Interface) Support (UNSUPPORTED)" if UNSUPPORTED
        depends on ARM_64
        ---help---
 
@@ -49,7 +49,7 @@ config GICV3
          If unsure, say Y
 
 config HAS_ITS
-        bool "GICv3 ITS MSI controller support" if EXPERT
+        bool "GICv3 ITS MSI controller support (UNSUPPORTED)" if UNSUPPORTED
         depends on GICV3 && !NEW_VGIC
 
 config HVM
@@ -104,7 +104,7 @@ config HARDEN_BRANCH_PREDICTOR
          If unsure, say Y.
 
 config TEE
-       bool "Enable TEE mediators support" if EXPERT
+       bool "Enable TEE mediators support (UNSUPPORTED)" if UNSUPPORTED
        default n
        help
          This option enables generic TEE mediators support. It allows guests

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 78f351f94b60f2d79af976716cdfae6487d92f5d..302334d3e44cd0385d84fc9b0e84fa97b846a078 100644 (file)
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -147,7 +147,7 @@ config BIGMEM
          If unsure, say N.
 
 config HVM_FEP
-       bool "HVM Forced Emulation Prefix support" if EXPERT
+       bool "HVM Forced Emulation Prefix support (UNSUPPORTED)" if UNSUPPORTED
        default DEBUG
        depends on HVM
        ---help---
@@ -166,7 +166,7 @@ config HVM_FEP
          If unsure, say N.
 
 config TBOOT
-       bool "Xen tboot support" if EXPERT
+       bool "Xen tboot support (UNSUPPORTED)" if UNSUPPORTED
        default y if !PV_SHIM_EXCLUSIVE
        select CRYPTO
        ---help---
@@ -252,7 +252,7 @@ config HYPERV_GUEST
 endif
 
 config MEM_SHARING
-       bool "Xen memory sharing support" if EXPERT
+       bool "Xen memory sharing support (UNSUPPORTED)" if UNSUPPORTED
        depends on HVM
 
 endmenu

diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index b5c91a16649ee915640120b8eb8f43a92223b06b..39451e83508af8e5a482ca7667c4523057bcf555 100644 (file)
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -272,7 +272,7 @@ config LATE_HWDOM
          If unsure, say N.
 
 config ARGO
-       bool "Argo: hypervisor-mediated interdomain communication" if EXPERT
+       bool "Argo: hypervisor-mediated interdomain communication (UNSUPPORTED)" if UNSUPPORTED
        ---help---
          Enables a hypercall for domains to ask the hypervisor to perform
          data transfer of messages between domains.

diff --git a/xen/common/sched/Kconfig b/xen/common/sched/Kconfig
index 61231aacaa1c755870cf3404e0169d795ed11af3..94c9e201392a1e0e0178911c366587baa63803c2 100644 (file)
--- a/xen/common/sched/Kconfig
+++ b/xen/common/sched/Kconfig
@@ -15,7 +15,7 @@ config SCHED_CREDIT2
          optimized for lower latency and higher VM density.
 
 config SCHED_RTDS
-       bool "RTDS scheduler support (EXPERIMENTAL)"
+       bool "RTDS scheduler support (UNSUPPORTED)" if UNSUPPORTED
        default y
        ---help---
          The RTDS scheduler is a soft and firm real-time scheduler for
@@ -23,14 +23,14 @@ config SCHED_RTDS
          in the cloud, and general low-latency workloads.
 
 config SCHED_ARINC653
-       bool "ARINC653 scheduler support (EXPERIMENTAL)"
+       bool "ARINC653 scheduler support (UNSUPPORTED)" if UNSUPPORTED
        default DEBUG
        ---help---
          The ARINC653 scheduler is a hard real-time scheduler for single
          cores, targeted for avionics, drones, and medical devices.
 
 config SCHED_NULL
-       bool "Null scheduler support (EXPERIMENTAL)"
+       bool "Null scheduler support (UNSUPPORTED)" if UNSUPPORTED
        default y
        ---help---
          The null scheduler is a static, zero overhead scheduler,