Re: [PATCH] sgx: Move sgx object from /machine/unattached to /machine

[Daniel P . Berrangé]

On Wed, Jan 12, 2022 at 10:16:33AM +0000, Peter Maydell wrote:
> On Wed, 12 Jan 2022 at 10:14, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > On Wed, Jan 12, 2022 at 11:55:17AM -0500, Yang Zhong wrote:
> > > When Libvirt start, it get the vcpu's unavailable-features from
> > > /machine/unattached/device[0] path by qom-get command, but in SGX
> > > guest, since the sgx-epc virtual device is initialized before VCPU
> > > creation(virtual sgx need set the virtual EPC info in the cpuid). This
> > > /machine/unattached/device[0] is occupied by sgx-epc device, which
> > > fail to get the unvailable-features from /machine/unattached/device[0].
> >
> > If libvirt decides to enable SGX in a VM, then surely it knows
> > that it should just query /machine/unattached/device[1] to get
> > the CPU features instead. Why do we need to do anything in QEMU ?
> 
> libvirt having to know it needs to look at /machine/unattached/device[n]
> for anything is a bit fragile, really... it's effectively encoding
> knowledge about what order things happen to get created inside QEMU.

So how do CPUs and other devices end up being under /unattached/ ?
Can we ensure that *all* QEMU devices have a well defined attachment
point ?

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|