emu: work around systemctl bad behavior

Signed-off-by: Robbie Harwood <rharwood@redhat.com>

0325-emu-linux-work-around-systemctl-kexec-returning.patch

@@ -0,0 +1,41 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Robbie Harwood <rharwood@redhat.com>
+Date: Wed, 22 Mar 2023 14:19:43 -0400
+Subject: [PATCH] emu/linux: work around systemctl kexec returning
+
+Per systemctl(1), it "is asynchronous; it will return after the reboot
+operation is enqueued, without waiting for it to complete".  This
+differs from kexec(8), which calls reboot(2) and therefore does not
+return.
+
+When not using fallback, this results in the confusing-but-harmless:
+
+    error trying to perform 'systemctl kexec': 0
+    Aborted. Press any key to exit.
+
+on screen for a bit, followed by successful kexec.
+
+To reduce the liklihood of hitting this case, add a delay on succesful
+return.  Ultimately, the systemd interface is racy: we can't avoid it
+entirely unless we never fallback on success.
+
+Signed-off-by: Robbie Harwood <rharwood@redhat.com>
+---
+ grub-core/loader/emu/linux.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/grub-core/loader/emu/linux.c b/grub-core/loader/emu/linux.c
+index 0cf378a376..7de3f7f861 100644
+--- a/grub-core/loader/emu/linux.c
++++ b/grub-core/loader/emu/linux.c
+@@ -74,6 +74,10 @@ grub_linux_boot (void)
+ 		(kexecute==1) ? "do-or-die" : "just-in-case");
+   rc = grub_util_exec (systemctl);
+ 
++  /* `systemctl kexec` is "asynchronous" and will return even on success. */
++  if (rc == 0)
++    grub_sleep (10);
++
+   if (kexecute == 1)
+     grub_fatal (N_("error trying to perform 'systemctl kexec': %d"), rc);
+ 

grub.patches

@@ -322,3 +322,4 @@ Patch0321: 0321-mm-Preallocate-some-space-when-adding-new-regions.patch
 Patch0322: 0322-mm-Avoid-complex-heap-growth-math-in-hot-path.patch
 Patch0323: 0323-hostdisk-work-around-proc-not-reporting-size.patch
 Patch0324: 0324-blscfg-check-for-mounted-boot-in-emu.patch
+Patch0325: 0325-emu-linux-work-around-systemctl-kexec-returning.patch

grub2.spec

@@ -17,7 +17,7 @@
 Name:		grub2
 Epoch:		1
 Version:	2.06
-Release:	89%{?dist}
+Release:	90%{?dist}
 Summary:	Bootloader with support for Linux, Multiboot and more
 License:	GPLv3+
 URL:		http://www.gnu.org/software/grub/
@@ -544,6 +544,9 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg
 %endif
 
 %changelog
+* Wed Mar 22 2023 Robbie Harwood <rharwood@redhat.com> - 2.06-90
+- emu: work around systemctl bad behavior
+
 * Thu Mar 09 2023 Robbie Harwood <rharwood@redhat.com> - 2.06-89
 - emu: handle BLS /boot weirdness