lib/bootloader: Write to PReP partition on ppc64le

lib/src/bootloader.rs

@@ -1,12 +1,34 @@
 use anyhow::Result;
-use camino::Utf8Path;
+use camino::{Utf8Path, Utf8PathBuf};
 use fn_error_context::context;
 
 use crate::blockdev::PartitionTable;
 use crate::task::Task;
 
 /// The name of the mountpoint for efi (as a subdirectory of /boot, or at the toplevel)
 pub(crate) const EFI_DIR: &str = "efi";
+pub(crate) const PREPBOOT_GUID: &str = "9E1A2D38-C612-4316-AA26-8B49521E5A8B";
+pub(crate) const PREPBOOT_LABEL: &str = "PowerPC-PReP-boot";
+
+/// Find the device to pass to bootupd. Only on powerpc64 right now
+/// we explicitly find one with a specific label.
+///
+/// This should get fixed once we execute on https://github.com/coreos/bootupd/issues/432
+fn get_bootupd_device(device: &PartitionTable) -> Result<Utf8PathBuf> {
+    #[cfg(target_arch = "powerpc64")]
+    {
+        return device
+            .partitions
+            .iter()
+            .find(|p| p.parttype.as_str() == PREPBOOT_GUID)
+            .ok_or_else(|| {
+                anyhow::anyhow!("Failed to find PReP partition with GUID {PREPBOOT_GUID}")
+            })
+            .map(|dev| dev.node.as_str().into());
+    }
+    #[cfg(not(target_arch = "powerpc64"))]
+    return Ok(device.path().into());
+}
 
 #[context("Installing bootloader")]
 pub(crate) fn install_via_bootupd(
@@ -17,7 +39,8 @@ pub(crate) fn install_via_bootupd(
     let verbose = std::env::var_os("BOOTC_BOOTLOADER_DEBUG").map(|_| "-vvvv");
     // bootc defaults to only targeting the platform boot method.
     let bootupd_opts = (!configopts.generic_image).then_some(["--update-firmware", "--auto"]);
-    let devpath = device.path();
+
+    let devpath = get_bootupd_device(device)?;
     let args = ["backend", "install", "--write-uuid"]
         .into_iter()
         .chain(verbose)

lib/src/install/baseline.rs

@@ -261,8 +261,8 @@ pub(crate) fn install_create_rootfs(
             &mut sgdisk.cmd,
             partno,
             "0:+4M",
-            "PowerPC-PReP-boot",
-            Some("9E1A2D38-C612-4316-AA26-8B49521E5A8B"),
+            crate::bootloader::PREPBOOT_LABEL,
+            Some(crate::bootloader::PREPBOOT_GUID),
         );
     } else {
         anyhow::bail!("Unsupported architecture: {}", std::env::consts::ARCH);