Add support for enabling Secure Encrypted Virtualization in the GUI

[Daniel P. Berrangé]

On Wed, Apr 20, 2022 at 09:11:27AM -0400, Cole Robinson wrote:
> On 4/19/22 1:21 PM, Daniel P. Berrangé wrote:
> > On Tue, Apr 19, 2022 at 12:05:29PM -0400, Cole Robinson wrote:
> >> On 4/4/22 11:49 AM, Charles Arnold wrote:
> >>>
> >>>
> >>> On 4/4/22 6:50 AM, Daniel P. Berrangé wrote:
> >>>> On Fri, Apr 01, 2022 at 12:13:17PM -0600, Charles Arnold wrote:
> >>>>>  From d700e8cee7cd525c0022b5a9a440f64c4ab149f0 Mon Sep 17 00:00:00 2001
> >>>>> From: Charles Arnold <carnold at suse.com>
> >>>>> Date: Fri, 1 Apr 2022 12:01:21 -0600
> >>>>> Subject: [PATCH 1/1] Add support for enabling Secure Encrypted
> >>>>> Virtualization
> >>>>>   in the GUI
> >>>>>
> >>>>> Add an "Enable Launch Security" checkbox on the Details memory tab.
> >>>>> Do the minimal configuration required for libvirt to enable this feature
> >>>>> on compatible hardware.
> >>>>>
> >>>> Don't we need to turn on the 'iommu' option for all virtio devices
> >>>> too, and disable PXE on any NICs ?
> >>>>
> >>>> https://libvirt.org/kbase/launch_security_sev.html#virtio
> >>>>
> >>>
> >>> I used to enumerate through the virtio devices in an old version of this
> >>> patch
> >>> for virt-manager and enable iommu but it really wasn't reasonable for
> >>> virt-manager to track which virtio devices needed iommu enabled.
> >>> Additionally,
> >>> libvirt will sometimes add a device when a VM is created. This patch
> >>> leans on libvirt to do the right thing when sev is enabled similar to what
> >>> happens when launch security is specified on the virt-install command line.
> >>>
> >>
> >> Yeah, I would still like to see libvirt do this unless there's a good
> >> reason why it can't. From my July 2020 mail
> >> https://listman.redhat.com/archives/virt-tools-list/2020-July/017087.html
> >>
> >>> if sev
> >>> launchSecurity _requires_ every virtio device to have iommu='on' then
> >>> libvirt should be setting that itself. It doesn't need to hardcode it
> >>> into the XML, it can set it at VM startup time. If the user set an
> >>> explicit value in the XML then honor that but otherwise fill it in at
> >>> runtime when it is required. Trying to deal with this in an app where we
> >>> want to advertise turning the config off is basically an impossible
> >>> problem to know if we are going to undo any explicit user config or not.
> >>
> >> danpb does this sound reasonable? If so I can work on this.
> > 
> > Something automagic sounds ok
> > 
> >> Also, anyone know if TDX and SNP will require virtio iommu setting as well?
> > 
> > I expect SNP will, but no idea about TDX.
> > 
> 
> So apparently qemu 6.0.0+ already does this for us:
> https://gitlab.com/qemu-project/qemu/-/commit/9f88a7a3df
> 
> Which is strange because some of my sev testing definitely failed with
> an iommu sounding error in the guest kernel until I enabled iommu on
> virtio-blk, but I can't reproduce now. Maybe I was using an older qemu,
> I think the host was fedora 34 at the time

Or you had new QEMU, but the guest was fixed on the older machine
type perhaps

With regards,
Daniel
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