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+++ This bug was initially created as a clone of Bug #1665400 +++
Description of problem:
Libvirt reports <sev supported='no'/> even though SEV is enabled on the platform, i.e. both the cpuflags contain 'sev' and /dev/sev exists on the filesystem.
Version-Release number of selected component (if applicable):
4.5.0-17.module+el8+2625+db702f9d
How reproducible:
Steps to Reproduce:
1. enable SEV on the platform so that /dev/sev appears on the filesystem
2. install libvirt, launch libvirtd
3. run virsh domcapabilities, the output contains:
...
<sev supported='no'/>
...
Actual results:
Libvirt is unable to launch a SEV VM because it reports the feature as unsupported
Expected results:
Libvirt is able to launch a SEV VM
Additional info:
1) Going through libvirt debug logs, one can also see that the error is coming from QEMU when probing for capabilities:
debug : qemuMonitorJSONIOProcessLine:197 : Line [{"id": "libvirt-53", "error": {"class": "GenericError", "desc": "SEV feature is not available"}}]
2) Even though 1) suggests this might be a bug in QEMU, the problem are the default permissions on /dev/sev:
# ls -l /dev/sev
crw-------. 1 root root
which is a problem because when libvirt probes QEMU for capabilities, the process runs as qemu:qemu by default.
There's been a turn of events in virt (libvirt+QEMU) which resulted in me starting an upstream discussion here:
https://www.redhat.com/archives/libvir-list/2019-January/msg00630.html which means that having an udev rule for /dev/sev might actually not turn up to be a good idea. It mainly depends on the input we get from AMD developers.
Closing as WONTFIX for now, since there is a potential security risk even with a 0644 rule at the moment. This needs to be addressed in kernel first. I'll reopen in the future if necessary.