[Pkg-xen-devel] Bug#820807: xen-hypervisor-4.4-amd64: Xen detects only one CPU when bootet via EFI and grub2

[Jörg Ludwig]

Package: xen-hypervisor-4.4-amd64
Version: 4.4.1-9+deb8u4
Severity: important

Dear Maintainer,

I installed a fresh Debian Jessie amd64 on our new server with Intel 
Xeon E3-1270 v5 Skylake CPU and EFI. Linux without Xen boots flawlessly 
and shows 8 CPU cores.

I then tried all combinations of Xen 4.4 (with xsave=off for Skylake 
support), Xen 4.6 (crashes after a few seconds during boot) and Xen 
4.6.1 (from OpenSuSE as there is not Debian package) with Linux 3.16.0-4 
and 4.4.0-0.bpo.1 booted via grub2. I any case only one CPU core was 
shown in "xl info" and "xl list".

As I found reports that EFI -> grub2 -> Xen has compatibility issues, I 
set up EFI to boot Xen directly without grub. This works flawlessly, all 
CPUs are shown. You can even leave the old grub installed and select it 
from the boot menu for maintenance.

I am posting this bug report to help anyone who runs into the same 
problem. I think this problem should at least be mentioned in the 
package description.

How to install Xen to EFI:
1. boot Linux without Xen (efibootmgr does not work inside Xen)
2. mkdir /boot/efi/EFI/Xen
3. copy initrd.img-3.16.0-4-amd64, vmlinuz-3.16.0-4-amd64 and 
xen-4.4-amd64.efi from /boot to /boot/efi/EFI/Xen
4. run: efibootmgr -w -L Xen -l "\EFI\Xen\xen-4.4-amd64.efi" -c
5. create /boot/efi/EFI/Xen/xen.cfg with the following content:

[global]
default=xen

[xen]
options=dom0_mem=512M xsave=off
kernel=vmlinuz-3.16.0-4-amd64 root=UUID=1234-5678 ro quiet
ramdisk=initrd.img-3.16.0-4-amd64

-- System Information:
Debian Release: 8.4
   APT prefers stable-updates
   APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/1 CPU core)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

xen-hypervisor-4.4-amd64 depends on no packages.

Versions of packages xen-hypervisor-4.4-amd64 recommends:
ii  xen-utils-4.4  4.4.1-9+deb8u4

xen-hypervisor-4.4-amd64 suggests no packages.

-- no debconf information

-- 
Mit freundlichen Grüßen,

Jörg Ludwig

IServ GmbH
Bültenweg 73
38106 Braunschweig

Telefon:     0531-2243666-0
Fax:         0531-2243666-9
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E-Mail:      joerg.ludwig at iserv.eu
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