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I would like some assistance filing two xen related bugs

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  I would like some assistance filing two xen related bugs Daniel Widenfalk <Daniel@lilla-graen.c.se> - 2020-06-28 13:50 +0200
    Re: I would like some assistance filing two xen related bugs Andy Smith <andy@strugglers.net> - 2020-06-29 01:40 +0200

#224141 — I would like some assistance filing two xen related bugs

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

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#224159

Hello,

On Sun, Jun 28, 2020 at 01:42:02PM +0200, Daniel Widenfalk wrote:
> 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.

Xen is a pretty fringe technology so I wouldn't expect there to be
much of a community of users and developers on debian-user. I use it
but don't have any useful input to your questions.

You can reach Debian's Xen maintainers on pkg-xen-devel:

    https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-xen-devel

but they are quite likely to refer you to upstream's xen-user or
xen-devel lists.

Cheers,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

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