kvm: add support for the bootindex property in bootable devices #1573
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This patch adds multiple device support for the boot_order setting. Valid values are still disk, cdrom, network and floppy, but the user can now supply a comma-separated list of those instead of a single value only. Additionally, this patch will now use the newer '-boot order=drives' syntax for the qemu command line, instead of the deprecated '-boot drives'.
This patch extends ganeti to support setting the bootindex property for bootable devices, namely disks, nics, cdroms and floppy. The bootindex property allows more fine-grained control of boot order preference, and supports multiple devices per device type (when booting via EFI).
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Update: If you want to test this patch (and #1605 #1604 #1572 as well), there's build instructions for bullseye here: https://github.com/modulus-sa/ganeti/wiki |
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This PR adds support for setting the bootindex property in all bootable devices currently managed by ganeti, namely disks, nics, cdroms and floppy drives. The bootindex property can be used for more fine-grained control of the boot order preference. AFAICT, the legacy
boot Xorboot order=Xqemu syntax relies on BIOS enumeration to determine the boot device, allowing one to effectively only deterministically specify a boot order preference for a specific device type, which is insufficient when a guest has multiple devices per type (e.g. two disks or two nics). BIOSes can still only boot from one device per device type (even with the bootindex property set), but UEFI implementations should be able to fail over to a device of the same type if the previous higher bootindex priority has failed.The primary motivation for writing this patch was to overcome boot failures encountered when passing storage devices through to the guest via methods bypassing ganeti storage management (i.e. using kvm_extra), but I expect it might be useful in other cases too, especially for UEFI guests. It builds upon #1572 and includes improvements included therein, but I can clean it up if needed.
Usage
size=128M,bootindex=0)link=br0,bootindex=1)Changes
In addition to changes needed to accommodate bootindex-related functionality, this PR also introduces the following:
if=virtiosyntax. The function now performs the same processing done for block devices:-drive ... -device ...syntax is now used-devicewill be set toscsi-cdwhich supports booting, hooked on avirtio-scsi-pcicontroller-global isa-fdc.syntax (more on that later)Caveats
MaybeInttype to accomodate Int or None for its values, but wasn't very successful (but some groundwork has been laid in this patch). Any help would be appreciated-global isa-fdc.syntax is deprecated. Unfortunately there seems to be some sort of bug when using the newer syntax (-device floppy,unit=0,drive=) which affects Windows guests (the floppy device is visible in explorer, but on accessing it one is presented with a cryptic error, there are reports of this online). The new cdrom device creation logic in this patch will render drives unreadable by windows guests when cdrom_disk_type is set to paravirtual, so in this case a working floppy implementation is needed to load the virtio drivers. I settled for using the legacy syntax supporting bootindex for floppies which also works with windows guests as a compromise.boot order=Nand bootindex options in the qemu cmdline at the same time. qemu documentation advises against this, but I haven't encountered any issues during (manual) testing. Having said that, I haven't tried conflicting options for these two methods (e.g. setting boot order to disk whilst having the highest bootindex priority set to a nic device). Thoughts?TODO
Successful manual testing so far:
Create an instance command and result:
gnt-instance add -t file -s 512M -o debootstrap+default --net 0:link=br0 -B memory=256M --no-start -n debtest.debtest.local -H kvm:kernel_path="/boot/vmlinuz-5.10.0-1-amd64" test1.debtest.localAdd bootindex to existing disk command and result
gnt-instance modify --disk 0:modify,bootindex=1 test1.debtest.localAdd bootindex to existing nic command and result:
gnt-instance modify --net 0:modify,bootindex=2 test1.debtest.localAdd cdrom image with bootindex command and result:
gnt-instance modify -H cdrom_image_path='/srv/ganeti/shared-file-storage/cd.iso',cdrom_bootindex=3 test1.debtest.localAdd floppy image with bootindex command and result:
gnt-instance modify -H floppy_image_path='/srv/ganeti/shared-file-storage/floppy.img',floppy_bootindex=4 test1.debtest.localAdd new disk with bootindex command and result:
gnt-instance modify --disk add:size=128M,bootindex=5 test1.debtest.localAdd new nic with bootindex command and result:
gnt-instance modify --net add:link=br0,bootindex=6 test1.debtest.localRemove bootindex from floppy command and result:
gnt-instance modify -H floppy_bootindex=-4 test1.debtest.localAdd cdrom2 image with bootindex command and result:
gnt-instance modify -H cdrom2_image_path='/srv/ganeti/shared-file-storage/cd2.iso',cdrom2_bootindex=8 test1.debtest.localChange cdrom_disk_type to ide command and result:
gnt-instance modify -H cdrom_disk_type=ide test1.debtest.local