On 02/01/2018 11:27 AM, Dr. David Alan Gilbert wrote:
* Brijesh Singh (brijesh.si...@amd.com) wrote:

On 1/30/18 2:08 PM, Dr. David Alan Gilbert wrote:
* Brijesh Singh (brijesh.si...@amd.com) wrote:
During machine creation we encrypted the guest bios image, the
LAUNCH_MEASURE command can be used to retrieve the measurement of
the encrypted memory region. Emit the SEV_MEASUREMENT event so that
libvirt can grab the measurement value as soon as we are done with
creating the encrypted machine.
Can you ust clarify what happens if the libvirt has disconnected and
reconnected to qemu and so didn't see the event?  Can the reconnecting
libvirt query it and find out it's ready/not ready yet?


I have not looked into details between libvirt and qemu interaction to
comment how and when the events will be delivered. Recently, one of my
colleague was implementing libvirt interface for the SEV guest and ran
into somewhat a similar challenge and posted question on libvirt mailing
list [1].

In previous discussion on qemu mailing list, we agreed to implement SEV
MEASUREMENT event which can be seen by libvirt. That's what this patch
is doing.

But during the libvirt implementation it seems that qemu monitor
silently drops all the events before it get the first qmp_capabilities
command. At a quick glance it seems on reconnect, libvirt issues
qmp_capabilities command and any event issued before the
qmp_capabilities command will never to delivered to libvirt. we are
looking for  help from libvirt/qemu monitor experts on how we solve this
problem. Our goal is to provide the measurement to libvirt before
libvirt issues "continue" command. Since event can't be seen by libvirt
before it resumes the guest hence I was wondering if we should we should
drop the SEV measurement event and consider adding a new QMP command to
query the SEV measurement.

Yep, I'll leave it to the libvirt contacts for the best way they'd like
to see that, as Eric says there's nothing wrong with having both the
command and event if useful.  Also keep in mind coping with a guest that
crashes early or that measurement never arrives.

Yep, lets see what libvirt experts say about it.

Hi Daniel,

Do you have any recommendation on whether we should consider adding a new QMP to retrieve the measurement or we do event or both? Please note that the launch measurement is generate only once for the lifetime of the guest. The measurement will be available after qmeu encrypts the guest bios during the machine initialization time.


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