On a Wednesday in 2020, Daniel Henrique Barboza wrote:
QEMU 4.1.0 introduced a new device type called TPM Proxy, currently implemented by PPC64 guests via a new virtual device called 'spapr-tpm-proxy' (see QEMU 0fb6bd073230 for more info).The TPM Proxy device interacts with a TPM Resource Manager, a host device capable of multiplexing the host TPM with multiple processes. This allows multiple guests to access some TPM features at the same time. Note that this mode of operation does not provide full TPM features to be available for the guest - for that case the guest still needs to assign a vTPM device (tpm-spapr for PPC64 guests). Although redundant, there is currently no technical limitation for a guest to assign both a vTPM and a TPM Proxy at the same time. This patch adds documentation and schema for a new TPM model type called 'spapr-tpm-proxy' that creates this new TPM Proxy device. This model is valid only for the 'passthrough' backend. An example of a TPM Proxy device connected to a TPM Resource Manager '/dev/tpmrm0' will look like this: <tpm model='spapr-tpm-proxy'> <backend type='passthrough'> <device path='/dev/tpmrm0'/> </backend> </tpm> Tested-by: Satheesh Rajendran <sathn...@linux.vnet.ibm.com> Reviewed-by: Stefan Berger <stef...@linux.ibm.com> Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com> --- docs/formatdomain.html.in | 19 ++++++++++++++++++- docs/schemas/domaincommon.rng | 1 + 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index 20c28a47e3..f538c3ff1a 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -8840,6 +8840,18 @@ qemu-kvm -net nic,model=? /dev/null backend device is a TPM 2.0. <span class="since">Since 6.1.0</span>, pSeries guests on PPC64 are supported and the default is <code>tpm-spapr</code>. + + <span class="since">Since 6.4.0</span>, a new model called
6.5.0
+ <code>spapr-tpm-proxy</code> was added for pSeries guests. This model
+ only works with the <code>passthrough</code> backend. It creates a
+ TPM Proxy device that communicates with an existing TPM Resource
Manager
+ in the host, for example <code>/dev/tpmrm0</code>, enabling the
guest to
+ run in secure virtual machine mode with the help of an Ultravisor.
Adding
+ a TPM Proxy to a pSeries guest brings no security benefits unless
the guest
+ is running on a PPC64 host that has an Ultravisor and a TPM Resource
Manager.
+ Only one TPM Proxy device is allowed per guest, but a TPM Proxy
device can
+ be added together with
+ other TPM devices.
</p>
</dd>
<dt><code>backend</code></dt>
@@ -8852,7 +8864,7 @@ qemu-kvm -net nic,model=? /dev/null
<dt><code>passthrough</code></dt>
<dd>
<p>
- Use the host's TPM device.
+ Use the host's TPM or TPM Resource Manager device.
</p>
<p>
This backend type requires exclusive access to a TPM device on
@@ -8860,6 +8872,11 @@ qemu-kvm -net nic,model=? /dev/null
qualified file name is specified by path attribute of the
<code>source</code> element. If no file name is specified then
/dev/tpm0 is automatically used.
+
+ <span class="since">Since 6.4.0</span>, when choosing the
6.5.0
+ <code>spapr-tpm-proxy</code> model, the file name specified is
+ expected to be a TPM Resource Manager device, e.g.
+ <code>/dev/tpmrm0</code>.
</p>
</dd>
</dl>
Reviewed-by: Ján Tomko <jto...@redhat.com> Jano
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