Unexplicable permission error when trying to read a qemu firmware file

[Emmanuel Kasper]

Hi

I want to create a CoreOS VM following the steps mentioned at
https://docs.fedoraproject.org/en-US/fedora-coreos/getting-started,
using a Debian 11 (bullseye) system.
I am thus creating a VM with the following virt-install command:

virt-install --connect="qemu:///system" --name=coreos \
    --vcpus=2 --memory=2048 \
    --os-variant=fedora29 --import --graphics=none \

--disk="size=10,backing_store=$PWD/fedora-coreos-33.20201201.3.0-qemu.x86_64.qcow2"
\
    --qemu-commandline="-fw_cfg
name=opt/com.coreos/config,file=/tmp/example.ign"

which spits some warnings and this mysterious error

2020-12-29T16:52:03.858938Z qemu-system-x86_64: warning: host doesn't
support requested feature: MSR(48FH).vmx-exit-load-perf-global-ctrl [bit 12]
2020-12-29T16:52:03.858941Z qemu-system-x86_64: warning: host doesn't
support requested feature: MSR(490H).vmx-entry-load-perf-global-ctrl
[bit 13]

2020-12-29T16:52:03.864778Z qemu-system-x86_64: -fw_cfg
name=opt/com.coreos/config,file=/tmp/example.ign: can't load
/tmp/example.ign: Failed to open file “/tmp/example.ign”: Permission denied

the file /tmp/example.ign is perfectly world readable,
-rw-rw-rw- 1 manu manu 1130 Dec 29 17:23 /tmp/example.ign

so I am puzzled at what could cause this permission error.

on a RHEL8 system, I had the same error, and was able to fix by setting
a security context on the firmware file:

sudo semanage fcontext --add --type virt_content_t /tmp/example.ign
restorecon /tmp/example.ign

now this Debian system does not selinux installed at all.
ls -dZ /
? /

I could also read the qemu firmware file when using the qemu:///session
connection

any pointers where to look for ?

Emmanuel