[pve-devel] [PATCH docs v2] add section about bios and uefi

[Dominik Csapak]

this section explains what is the default and why,
and explains when you need ovmf and why you need an efidisk

also we explain how you can create an efidisk and that you
have to set the resolution in the ovmf menu

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
changes from v1:
 * made the last sentence of the first paragraph less redundant
 * typo

 qm.adoc | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/qm.adoc b/qm.adoc
index 375cc39..5d0225d 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -368,6 +368,38 @@ if you use a SPICE client which supports it. If you add a SPICE USB port
 to your VM, you can passthrough a USB device from where your SPICE client is,
 directly to the VM (for example an input device or hardware dongle).
 
+BIOS and UEFI
+~~~~~~~~~~~~~
+
+In order to properly emulate a computer, QEMU needs to use a firmware.
+By default QEMU uses *SeaBIOS* for this, which is an open-source, x86 BIOS
+implementation. SeaBIOS is a good choice for most standard setups.
+
+There are, however, some scenarios in which a BIOS is not a good firmware
+to boot from, e.g. if you want to do VGA passthrough. footnote:[Alex Williamson has a very good blog entry about this.
+http://vfio.blogspot.co.at/2014/08/primary-graphics-assignment-without-vga.html]
+In such cases, you should rather use *OVMF*, which is an open-source UEFI implemenation. footnote:[See the OVMF Project http://www.tianocore.org/ovmf/]
+
+If you want to use OVMF, there are several things to consider:
+
+In order to save things like the *boot order*, there needs to be an EFI Disk.
+This disk will be included in backups and snapshots, and there can only be one.
+
+You can create such a disk with the following command:
+
+ qm set <vmid> -efidisk0 <storage>:1,format=<format>
+
+Where *<storage>* is the storage where you want to have the disk, and
+*<format>* is a format which the storage supports. Alternatively, you can
+create such a disk through the web interface with 'Add' -> 'EFI Disk' in the
+hardware section of a VM.
+
+When using OVMF with a virtual display (without VGA passthrough),
+you need to set the client resolution in the OVMF menu(which you can reach
+with a press of the ESC button during boot), or you have to choose
+SPICE as the display type.
+
+
 Managing Virtual Machines with 'qm'
 ------------------------------------
 
-- 
2.1.4