virtualization/config: allow conditional use of yocto-cfg-fragments

To help enforce/guide consistent configuration and to avoid duplicating
configuration fragments into the meta-virt layer, we leverage a native
provider of the yocto-kernel-cache fragment repository.

To allow support for kernels that support fragments, but don't have the
yocto-kernel-cache in the kernel's SRC_URI, we create two conditional
parts of the virtualization configuration.

If virtualization is enabled in the distro features, the kernel
version matches one of our supported ones, and the kernel inherits
kernel-yocto, we add a depedency on the yocto-cfg-fragments-native
recipe.

That recipe will install the fragment collection to the kernel recipe's
native sysroot.

We can then check for the kernel-cache on the SRC_URI. If it is present,
we use the feature at the standard location. If it is not present, we
add the fragment from the native sysroot.

While we could always use the native sysroot variant, we want to allow
a kernel with a kernel-cache to be the first choice, and provide their
own fragments.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/recipes-kernel/linux/linux-yocto_virtualization.inc b/recipes-kernel/linux/linux-yocto_virtualization.inc
index 321dda20..4c6dc42f 100644
--- a/recipes-kernel/linux/linux-yocto_virtualization.inc
+++ b/recipes-kernel/linux/linux-yocto_virtualization.inc
@@ -15,11 +15,30 @@ KERNEL_MODULE_AUTOLOAD += "${@bb.utils.contains('DISTRO_FEATURES', 'kvm', 'kvm',
 # aufs kernel support required for xen-image-minimal
 KERNEL_FEATURES_append += "${@bb.utils.contains('DISTRO_FEATURES', 'aufs', ' features/aufs/aufs-enable.scc', '', d)}"
 
-KERNEL_FEATURES_append = " cfg/virtio.scc"
+# if the kernel-yocto meta-data routine automatically starts to add the
+# recipe-sysroot-native, we can do away with this conditional, since all
+# features will be found at the same relative offset from a search
+# directory
+def kernel_cache_cond_feature(src_uri,feature):
+    import re
+    kernel_cache = re.search("kernel-cache", src_uri )
+    if kernel_cache:
+       return feature
+
+    return "../recipe-sysroot-native/kcfg/" + feature
+
+KERNEL_CACHE_FEATURES ?= "${@kernel_cache_cond_feature(d.getVar('SRC_URI'),'cfg/virtio.scc')}"
+KERNEL_FEATURES_append = "${KERNEL_CACHE_FEATURES}"
+
+# if kernel-yocto has been inherited (how we can check for configuration
+# fragment merging suport at the moment, then add a dependency on the
+# configuration fragment repository. This allows us to be sure that our
+# features can be enabled via the fragments
+do_kernel_metadata[depends] += "${@['', 'yocto-cfg-fragments-native:do_populate_sysroot'][(bb.data.inherits_class('kernel-yocto', d))]}" 
 
 # xen kernel support
 SRC_URI += "${@bb.utils.contains('DISTRO_FEATURES', 'xen', ' file://xen.scc', '', d)}"
 
 # k8s and k3s kernel support
 SRC_URI += "${@bb.utils.contains('DISTRO_FEATURES', 'k8s', ' file://kubernetes.scc', '', d)}"
-SRC_URI += "${@bb.utils.contains('DISTRO_FEATURES', 'k3s', ' file://kubernetes.scc', '', d)}"
\ No newline at end of file
+SRC_URI += "${@bb.utils.contains('DISTRO_FEATURES', 'k3s', ' file://kubernetes.scc', '', d)}"