Re: [PATCH 3/6] qemu: check if AMD secure guest support is enabled

>>>> 2) check if /dev/sev device exist (aka firmware is detected) >>> This seems reasonable. Shouldn't it have been documented in >>> docs/kbase/launch_security_sev.rst? >> Sure, we can add a mention about this. Although, doesn't 1 imply 2? IOW can >> you have the kernel module parameter set to 1 and yet kernel doesn't expose the >> /dev/sev node? > > Currently, 1 does not imply 2, KVM driver does not initialize the > firmware during the feature probe (i.e does not access the /dev/sev). > The firmware initialization is delayed until the first guest launch. So > only sane way to know whether firmware is been detected is check the > existence of the /dev/sev or issue a query-sev command . The query-sev > command will send the platform_status request to the firmware, if the > firmware is not ready then this command will fail. I see. Can query-sev fail or return that it's disabled, aka {"enabled": false,...} in the SevInfo QMP response, but at the same time succeed in returning the platform capabilities via query-sev-capabilities? I'm asking, because libvirt only issues the latter to fill in the QEMU capabilities structure.