Splitting off from

 Bug 956526 - PANIC on Xen Dom0 restart
 https://bugzilla.suse.com/show_bug.cgi?id=956526

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 Michael Chang 2015-11-26 08:35:53 UTC

I think a patch like this would allow to set xen loader options via, say, 
SUSE_EFI_XEN_LOADER_CMDLINE="-mapbs" in /etc/default/grub. But we'd better not
to invent new settings if not required. So I'm support Andrei's suggestion,
better to clarify why -mapbps is needed or is supported and possibility to
detect it as part of auto configuration settings.

Index: grub-2.02~beta2/util/grub-mkconfig.in
===================================================================
--- grub-2.02~beta2.orig/util/grub-mkconfig.in
+++ grub-2.02~beta2/util/grub-mkconfig.in
@@ -260,7 +260,8 @@ export GRUB_DEFAULT \
   GRUB_DISABLE_SUBMENU \
   GRUB_CMDLINE_LINUX_RECOVERY \
   GRUB_USE_LINUXEFI \
-  SUSE_BTRFS_SNAPSHOT_BOOTING
+  SUSE_BTRFS_SNAPSHOT_BOOTING \
+  SUSE_EFI_XEN_LOADER_CMDLINE

 if test "x${grub_cfg}" != "x"; then
   rm -f "${grub_cfg}.new"
Index: grub-2.02~beta2/util/grub.d/20_linux_xen.in
===================================================================
--- grub-2.02~beta2.orig/util/grub.d/20_linux_xen.in
+++ grub-2.02~beta2/util/grub.d/20_linux_xen.in
@@ -176,7 +176,7 @@ linux_entry ()
     message="$(gettext_printf "Loading Xen %s with Linux %s ..."
${xen_version} ${version})"
     sed "s/^/$submenu_indentation/" <<-EOF
                echo    '$(echo "$message" | grub_quote)'
-               chainloader  \$cmdpath/${xen_basename} ${xen_basename} $section
+               chainloader  \$cmdpath/${xen_basename} ${xen_basename} $section
${SUSE_EFI_XEN_LOADER_CMDLINE}
        }
        EOF
     for f in ${grub_dir}/$xen_cfg ${xen_dir}/${xen_basename}
${rel_dirname}/${basename} ${rel_dirname}/${initrd}; do
------------
 boo35 boo35 2015-11-26 14:12:31 UTC

Note that there are other EFI flags that are available/useful.

E.g., in the Xen thread alone are mentioned

  /basevideo, /mapbs, noexitboot & /query

I'd guess a longer list can be extracted from the tiaonocore sources.  I'm not
sure which vendors are using the tiaonocore UEFI vs. 'other'.

Although auto-detection may be possible, for which failure?  Only one? More?

Trying to identify all cases of failure, and all possible flag-combo solutions
isn't a tenable solution.

The flexibility to have the enduser diagnose (nrokennesss, performances issue,
etc), and add flags to config -- as is currently often done for both Kernel &
Xen 
is imo preferable.  The "SUSE_EFI_XEN_LOADER_CMDLINE" string seems a simple
enough approach.

If/when grub@suse and grub@upstream coordinate, pushing that cmdline upstream
makes sense.

Of course, getting EFI fixed is the best solution; I've already contacted the
H/W vendor, and they're working on this issue.
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