Re: [pve-devel] [PATCH qemu-server 02/14] blockdev: cmdline: convert drive to blockdev syntax

[Fiona Ebner <f.ebner@proxmox.com>]

Am 12.05.25 um 17:33 schrieb DERUMIER, Alexandre:
> -
>> (for example, they are an "size" option on drive not existing on
>> blockdev for example, I have wrote details on the patch 3/14.)
> 
>>> I do think we still need the size (would need to be tested), because
>>> OVMF would get confused when the image is padded/too large. The
>>> commit
>>> message for 818ce80ec1a89c4abee61145c858b9323180e31b you mention in
>>> 03/14 describes this.
> 
>>> We might need to use a similar approach as proposed in
> i.e. using
>>> FUSE/NBD export for such images. Alternatively we could check how
>>> difficult it would be to add a size setting for blockdev.
> 
> 
> I have checked the qemu code, it seem that the raw driver have a size
> && offset parameters
> 
> They are some examples with nbd export
> 
> in qemu changelog:
> 
> "5. Exporting a partition can still be done by utilizing the --image-
> opts option with a raw blockdev using the offset and size parameters
> layered on top of any other existing blockdev.
> For example, if partition 1 is 100MiB long starting at 1MiB, the old
> command:
> qemu-nbd -t -P 1 -f qcow2 file.qcow2
> 
> --->
> 
> qemu-nbd -t --image-opts
> driver=raw,offset=1M,size=100M,file.driver=qcow2,file.file.driver=file,
> file.file.filename=file.qcow2
> "
> 
> or in
> https://github.com/qemu/qemu/blob/7be29f2f1a3f5b037d27eedbd5df9f441e8c8c16/docs/tools/qemu-nbd.rst#L248
> 
> "
> qemu-nbd \
>   --object tls-creds-x509,id=tls0,endpoint=server,dir=/path/to/qemutls
> \
>   --object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,\
>             O=Example Org,,L=London,,ST=London,,C=GB' \
>   --tls-creds tls0 --tls-authz auth0 \
>   -t -x subset -p 10810 \
>   --image-opts
> driver=raw,offset=1M,size=1M,file.driver=file,file.filename=file.raw
> "
> 
> 
> libvirt implementation:
> https://patchew.org/Libvirt/cover.1579193759.git.pkrempa@redhat.com/4b8e0bd263f8f4a63e0c124eda9d21d02fbd55f4.1579193759.git.pkrempa@redhat.com/
> 
> 
> 
> Seem that it can be set directly in the format node if it's raw, or
> like a filter node before the format node

Right, so for EFI, we don't need an export and just set the size
directly with the raw driver :) We don't need to do any special handling
for qcow2 (we already don't do any special handling right now), because
there, we already allocate with the correct virtual size.

https://qemu.readthedocs.io/en/master/interop/qemu-qmp-ref.html#object-QMP-block-core.BlockdevOptionsRaw


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