[PATCH v3 3/4] meta: Support opting out of any machine features

Paul Barker
2026-04-01T17:42:15Z

Add default values to MACHINE_FEATURES using the new
filter_default_features() function.

This change obsoletes the variables MACHINE_FEATURES_BACKFILL and
MACHINE_FEATURES_BACKFILL_CONSIDERED. Instead, all defaults are added
via MACHINE_FEATURES_DEFAULTS and users can opt out of any of these
using MACHINE_FEATURES_OPTED_OUT. Hopefully the variable naming here is
easier for people to understand and remember.

Migration notes:

- MACHINE_FEATURES will now get the default features added
automatically. You will need to review these and add any features you
do not want to use to MACHINE_FEATURES_OPTED_OUT.

- If you previously set MACHINE_FEATURES_BACKFILL_CONSIDERED, use the new
variable MACHINE_FEATURES_OPTED_OUT instead.

- If you previously modified MACHINE_FEATURES_BACKFILL, don't do that.

Signed-off-by: Paul Barker <paul@pbarker.dev>
---
meta/classes-global/base.bbclass | 4 +---
meta/classes-recipe/nativesdk.bbclass | 1 -
meta/conf/bitbake.conf | 2 +-
meta/conf/documentation.conf | 4 ++--
meta/conf/machine/include/mips/arch-mips.inc | 2 +-
meta/conf/machine/include/powerpc/tune-power5.inc | 2 +-
meta/conf/machine/include/powerpc/tune-power6.inc | 2 +-
meta/conf/machine/include/powerpc/tune-power7.inc | 2 +-
meta/conf/machine/include/powerpc/tune-ppce5500.inc | 2 +-
meta/conf/machine/include/powerpc/tune-ppce6500.inc | 2 +-
meta/conf/machine/include/x86/arch-x86.inc | 2 +-
11 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/meta/classes-global/base.bbclass b/meta/classes-global/base.bbclass
index 0a4cfd594c72..76fd0ac046a9 100644
--- a/meta/classes-global/base.bbclass
+++ b/meta/classes-global/base.bbclass
@@ -457,9 +457,7 @@ python () {
# Filter default features to allow users to opt out of features they don't
# want.
oe.utils.filter_default_features("DISTRO_FEATURES", d)
-
- # Handle backfilling
- oe.utils.features_backfill("MACHINE_FEATURES", d)
+ oe.utils.filter_default_features("MACHINE_FEATURES", d)

# To add a recipe to the skip list , set:
# SKIP_RECIPE[pn] = "message"
diff --git a/meta/classes-recipe/nativesdk.bbclass b/meta/classes-recipe/nativesdk.bbclass
index a4801c48b2de..80f716fc3c34 100644
--- a/meta/classes-recipe/nativesdk.bbclass
+++ b/meta/classes-recipe/nativesdk.bbclass
@@ -17,7 +17,6 @@ CLASSOVERRIDE = "class-nativesdk"
MACHINEOVERRIDES = ""

MACHINE_FEATURES = "${SDK_MACHINE_FEATURES}"
-MACHINE_FEATURES_BACKFILL = ""

MULTILIBS = ""

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index f851e2adc9f7..84450386d984 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -912,7 +912,7 @@ DISTRO_FEATURES_NATIVESDK:mingw32 = "x11 ipv6"
DISTRO_FEATURES_FILTER_NATIVE ?= "api-documentation debuginfod opencl opengl wayland"
DISTRO_FEATURES_FILTER_NATIVESDK ?= "api-documentation debuginfod opencl opengl wayland"

-MACHINE_FEATURES_BACKFILL = "rtc qemu-usermode"
+MACHINE_FEATURES_DEFAULTS = "rtc qemu-usermode"

COMBINED_FEATURES = "${@oe.utils.set_intersect('DISTRO_FEATURES', 'MACHINE_FEATURES', d)}"
COMBINED_FEATURES[vardeps] += "DISTRO_FEATURES MACHINE_FEATURES"
diff --git a/meta/conf/documentation.conf b/meta/conf/documentation.conf
index 5c93d0e47970..3c2088754188 100644
--- a/meta/conf/documentation.conf
+++ b/meta/conf/documentation.conf
@@ -277,8 +277,8 @@ MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS[doc] = "A list of recommended machine-specif
MACHINE_EXTRA_RDEPENDS[doc] = "A list of machine-specific packages to install as part of the image being built that are not essential for the machine to boot. However, the build process for more fully-featured images depends on the packages being present."
MACHINE_EXTRA_RRECOMMENDS[doc] = "A list of machine-specific packages to install as part of the image being built that are not essential for booting the machine. The image being built has no build dependencies on the packages in this list."
MACHINE_FEATURES[doc] = "Specifies the list of hardware features the MACHINE supports."
-MACHINE_FEATURES_BACKFILL[doc] = "Features to be added to MACHINE_FEATURES if not also present in MACHINE_FEATURES_BACKFILL_CONSIDERED. This variable is set in the meta/conf/bitbake.conf file and is not intended to be user-configurable."
-MACHINE_FEATURES_BACKFILL_CONSIDERED[doc] = "Features from MACHINE_FEATURES_BACKFILL that should not be backfilled (i.e. added to MACHINE_FEATURES) during the build."
+MACHINE_FEATURES_DEFAULTS[doc] = "The default set of machine features, prior to any filtering. Usually you should leave this alone and modify MACHINE_FEATURES and/or MACHINE_FEATURES_OPTED_OUT."
+MACHINE_FEATURES_OPTED_OUT[doc] = "The set of default machine features to disable. Prefer opting out of features using this variable instead of using MACHINE_FEATURES:remove."
MACHINEOVERRIDES[doc] = "Lists overrides specific to the current machine. By default, this list includes the value of MACHINE."
MAINTAINER[doc] = "The email address of the distribution maintainer."
MIRRORS[doc] = "Specifies additional paths from which the OpenEmbedded build system gets source code."
diff --git a/meta/conf/machine/include/mips/arch-mips.inc b/meta/conf/machine/include/mips/arch-mips.inc
index baadc61d652c..fff2ff639279 100644
--- a/meta/conf/machine/include/mips/arch-mips.inc
+++ b/meta/conf/machine/include/mips/arch-mips.inc
@@ -21,7 +21,7 @@ ABIEXTENSION .= "${@bb.utils.filter('TUNE_FEATURES', 'n32', d)}"
TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'n32', ' -mabi=n32', '', d)}"

# user mode qemu doesn't support mips64 n32: "Invalid ELF image for this architecture"
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = " ${@bb.utils.contains('TUNE_FEATURES', 'n32', 'qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'n32', 'qemu-usermode', '', d)}"

TUNEVALID[n64] = "MIPS64 n64 ABI"
TUNECONFLICTS[n64] = "o32 n32"
diff --git a/meta/conf/machine/include/powerpc/tune-power5.inc b/meta/conf/machine/include/powerpc/tune-power5.inc
index e70e4012176c..452897d2d43d 100644
--- a/meta/conf/machine/include/powerpc/tune-power5.inc
+++ b/meta/conf/machine/include/powerpc/tune-power5.inc
@@ -21,4 +21,4 @@ GLIBC_EXTRA_OECONF:powerpc64 += "${@bb.utils.contains('TUNE_FEATURES', 'power5',
GLIBC_EXTRA_OECONF:powerpc += "${@bb.utils.contains('TUNE_FEATURES', 'power5', '--with-cpu=power5', '', d)}"

# QEMU usermode fails with invalid instruction error
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = "${@bb.utils.contains('TUNE_FEATURES', 'power5', ' qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'power5', 'qemu-usermode', '', d)}"
diff --git a/meta/conf/machine/include/powerpc/tune-power6.inc b/meta/conf/machine/include/powerpc/tune-power6.inc
index eaf89515cad7..da8831058094 100644
--- a/meta/conf/machine/include/powerpc/tune-power6.inc
+++ b/meta/conf/machine/include/powerpc/tune-power6.inc
@@ -21,4 +21,4 @@ GLIBC_EXTRA_OECONF:powerpc64 += "${@bb.utils.contains('TUNE_FEATURES', 'power6',
GLIBC_EXTRA_OECONF:powerpc += "${@bb.utils.contains('TUNE_FEATURES', 'power6', '--with-cpu=power6', '', d)}"

# QEMU usermode fails with invalid instruction error
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = "${@bb.utils.contains('TUNE_FEATURES', 'power6', ' qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'power6', 'qemu-usermode', '', d)}"
diff --git a/meta/conf/machine/include/powerpc/tune-power7.inc b/meta/conf/machine/include/powerpc/tune-power7.inc
index 4531ddd85f48..47887c553f97 100644
--- a/meta/conf/machine/include/powerpc/tune-power7.inc
+++ b/meta/conf/machine/include/powerpc/tune-power7.inc
@@ -21,4 +21,4 @@ GLIBC_EXTRA_OECONF:powerpc64 += "${@bb.utils.contains('TUNE_FEATURES', 'power7',
GLIBC_EXTRA_OECONF:powerpc += "${@bb.utils.contains('TUNE_FEATURES', 'power7', '--with-cpu=power7', '', d)}"

# QEMU usermode fails with invalid instruction error
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = "${@bb.utils.contains('TUNE_FEATURES', 'power7', ' qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'power7', 'qemu-usermode', '', d)}"
diff --git a/meta/conf/machine/include/powerpc/tune-ppce5500.inc b/meta/conf/machine/include/powerpc/tune-ppce5500.inc
index 446b344c3d25..63e745b4a29c 100644
--- a/meta/conf/machine/include/powerpc/tune-ppce5500.inc
+++ b/meta/conf/machine/include/powerpc/tune-ppce5500.inc
@@ -19,4 +19,4 @@ PACKAGE_EXTRA_ARCHS:tune-ppc64e5500 = "${PACKAGE_EXTRA_ARCHS:tune-powerpc64} ppc
QEMU_EXTRAOPTIONS:tune-ppc64e5500 = " -cpu e500mc"

# QEMU usermode fails with invalid instruction error (YOCTO: #10304)
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = "${@bb.utils.contains('TUNE_FEATURES', 'e5500', ' qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'e5500', 'qemu-usermode', '', d)}"
diff --git a/meta/conf/machine/include/powerpc/tune-ppce6500.inc b/meta/conf/machine/include/powerpc/tune-ppce6500.inc
index 4444705b2d6d..77de2f9982bc 100644
--- a/meta/conf/machine/include/powerpc/tune-ppce6500.inc
+++ b/meta/conf/machine/include/powerpc/tune-ppce6500.inc
@@ -19,4 +19,4 @@ PACKAGE_EXTRA_ARCHS:tune-ppc64e6500 = "${PACKAGE_EXTRA_ARCHS:tune-powerpc64} ppc
QEMU_EXTRAOPTIONS:tune-ppc64e6500 = " -cpu e500mc"

# QEMU usermode fails with invalid instruction error (YOCTO: #10304)
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = "${@bb.utils.contains('TUNE_FEATURES', 'e6500', ' qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'e6500', 'qemu-usermode', '', d)}"
diff --git a/meta/conf/machine/include/x86/arch-x86.inc b/meta/conf/machine/include/x86/arch-x86.inc
index 28742e794d63..95b5fe52114c 100644
--- a/meta/conf/machine/include/x86/arch-x86.inc
+++ b/meta/conf/machine/include/x86/arch-x86.inc
@@ -25,7 +25,7 @@ TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'mx32', ' -mx32', '', d)}"
TUNE_LDARGS += "${@bb.utils.contains('TUNE_FEATURES', 'mx32', '-m elf32_x86_64', '', d)}"
TUNE_ASARGS += "${@bb.utils.contains('TUNE_FEATURES', 'mx32', '-x32', '', d)}"
# user mode qemu doesn't support x32
-MACHINE_FEATURES_BACKFILL_CONSIDERED:append = " ${@bb.utils.contains('TUNE_FEATURES', 'mx32', 'qemu-usermode', '', d)}"
+MACHINE_FEATURES_OPTED_OUT += "${@bb.utils.contains('TUNE_FEATURES', 'mx32', 'qemu-usermode', '', d)}"
MACHINEOVERRIDES =. "${@bb.utils.contains('TUNE_FEATURES', 'mx32', 'x86-x32:', '', d)}"

# ELF64 ABI

--
2.43.0