Hi,
Four years ago I ran into two issues with the xen support in Debian - at
that time I forgot to report these issues back to Debian. Now, when
setting up a new machine I ran into the second of these issues (and it
turned out that the first one was still there).
Scenario: An Amd 3700X CPU on a X570 based motherboard
1) Using EFI boot will incorrectly add "no-real-mode edd=off" to the
kernel (xen) command line:
For me this manifested (four years ago) as not getting a working
console. Digging around it turned out that the GRUB script generator
(20_linux_xen) emitted code that checked if $grub_platform was either
"pc" or "". When using EFI boot this variable gets set to "efi". This
mismatch causes the script to add "no-real-mode edd=off" to the command
line.
In latest stable Debian this works, although it still adds those two
kernel (xen) command line options. The fix is very simple:
--- /etc/grub.d/20_linux_xen~ 2020-06-28 12:37:08.394067050 +0200
+++ /etc/grub.d/20_linux_xen 2020-06-28 12:41:46.056439654 +0200
@@ -125,7 +125,7 @@
lmessage="$(gettext_printf "Loading Linux %s ..." ${version})"
sed "s/^/$submenu_indentation/" << EOF
echo '$(echo "$xmessage" | grub_quote)'
- if [ "\$grub_platform" = "pc" -o "\$grub_platform" = "" ]; then
+ if [ "\$grub_platform" = "pc" -o "\$grub_platform" = "efi" -o
"\$grub_platform" = "" ]; then
xen_rm_opts=
else
xen_rm_opts="no-real-mode edd=off"
2) CPU frequency scaling does not seem to work.
This one was a bit trickier to figure out. You can see my mail (from
2016) to the xen users mailing list here:
http://xen.1045712.n5.nabble.com/CPU-frequency-scaling-there-be-dragons-here-td5732214.html
The core issue is that the xen-acpi-processor module is not loaded
during boot which in turn causes the xen/drivers/cpufreq stuff to not
get initialized. Again, the fix was very simple - just add
xen-acpi-processor to /etc/modules. I guess this should be done whenever
installing the xen hypervisor?
I would very much appreciate some quick pointers on how to properly
report this so that I don't have to dig up my posts to the xen users
mailing list to figure out something I already should know.
/D
