11:53 a.m.
This patch series provides support for launching an encrypted guest using
AMD's new Secure Encrypted Virtualization (SEV) feature.
SEV is an extension to the AMD-V architecture which supports running
multiple VMs under the control of a hypervisor. When enabled, SEV feature
allows the memory contents of a virtual machine (VM) to be transparently
encrypted with a key unique to the guest VM.
In order to launch SEV guest we need QEMU SEV patch [1].
[1] https://marc.info/?l=kvm&m=151871349515849&w=2
The patch series implements some of recommendation from Daniel [2]
[2] https://www.redhat.com/archives/libvir-list/2017-September/msg00197.html
At very high level the flow looks this:
1. mgmt tool calls virConnectGetDomainCapabilities. This returns an XML document
that includes the following
<feature>
...
<sev supported='yes'>
<cbitpos> </cbitpos>
<reduced-phys-bits> </reduced-phys-bits>
<pdh> </pdh>
<cert-chain> </cert-chain>
</feature>
If <sev> is provided then we indicate that hypervisor is capable of launching
SEV guest.
2. (optional) mgmt tool can provide the PDH and Cert-chain to guest owner in case
if guest owner wish to establish a secure connection with SEV firmware to
negotiate a key used for validating the measurement.
3. mgmt tool requests to start a guest calling virCreateXML(), passing
VIR_DOMAIN_START_PAUSED.
The xml would include
<sev>
<cbitpos> </cbitpos> /* the value is same as what is obtained via
virConnectGetDomainCapabilities()
<reduced-phys-bits> </reduced-phys-bits> /* the value is same as what is
obtained via virConnectGetDomainCapabilities()
<dh-cert> .. </dh> /* guest owners diffie-hellman key */ (optional)
<session> ..</session> /* guest owners session blob */ (optional)
<policy> ..</policy> /* guest policy */ (optional)
4. Libvirt generate the QEMU cli arg to enable the SEV feature, a typical
args looks like this:
# $QEMU ..
-machine memory-encryption=sev0 \
-object sev-guest,id=sev0,dh-cert-file=<file>....
5. Libvirt generates lifecycle VIR_DOMAIN_EVENT_SUSPENDED_PAUSED event
6. mgmt tool gets the VIR_DOMAIN_EVENT_SUSPENDED_PAUSED and calls
virDomainGetSevVmMeasurement()
to retrieve the measurement of encrypted memory.
7. (optional) mgmt tool can provide the measurement value to guest owner, which can
validate the measurement and gives GO/NO-GO answer. If mgmt tool gets GO then
it resumes the guest otherwise it calls destroy() to kill the guest.
8. mgmt tool resumes the guest
TODO:
* SEV guest require to use DMA apis for the virtio devices. In order to use the DMA
apis the virtio devices must have this tag
<driver iommu=on ats=on>
It is a bit unclear to me where these changes need to go. Do we need to
modify the libvirt to automatically add these when SEV is enabled or
we ask mgmt tool to make sure that it creates XML with right tag to enable
the DMA APIs for virtio devices. I am looking for some suggestions.
Using these patches we have succesfully booted and tested a guest both with and
without SEV enabled.
SEV Firmware API spec is available at:
https://support.amd.com/TechDocs/55766_SEV-KM%20API_Specification.pdf
Brijesh Singh (4):
qemu: provide support to query the SEV capability
qemu: introduce SEV feature in hypervisor capabilities
conf: introduce sev element in domain
libvirt-domain: add new virDomainGetSevVmMeasurement() API
docs/formatdomain.html.in | 71 ++++++++++++++++++++++
docs/formatdomaincaps.html.in | 31 ++++++++++
docs/schemas/domaincaps.rng | 10 ++++
include/libvirt/libvirt-domain.h | 4 ++
src/conf/domain_capabilities.c | 19 ++++++
src/conf/domain_capabilities.h | 25 ++++++++
src/conf/domain_conf.c | 64 ++++++++++++++++++++
src/conf/domain_conf.h | 18 ++++++
src/driver-hypervisor.h | 4 ++
src/libvirt-domain.c | 41 +++++++++++++
src/libvirt_public.syms | 1 +
src/qemu/qemu_capabilities.c | 69 +++++++++++++++++++++-
src/qemu/qemu_capspriv.h | 4 ++
src/qemu/qemu_command.c | 77 ++++++++++++++++++++++++
src/qemu/qemu_driver.c | 51 ++++++++++++++++
src/qemu/qemu_monitor.c | 17 ++++++
src/qemu/qemu_monitor.h | 6 ++
src/qemu/qemu_monitor_json.c | 124 +++++++++++++++++++++++++++++++++++++++
src/qemu/qemu_monitor_json.h | 5 ++
19 files changed, 640 insertions(+), 1 deletion(-)
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2.14.3