Re: [libvirt] [PATCH] Add new 'kvm' domain feature and ability to hide KVM signature

On 08/15/2014 12:32 PM, Alex Williamson wrote: > QEMU 2.1 added support for the kvm=off option to the -cpu command, > allowing the KVM hypervisor signature to be hidden from the guest. > This enables disabling of some paravirualization features in the > guest as well as allowing certain drivers which test for the > hypervisor to load. Domain XML syntax is as follows: > > <domain type='kvm> > ... > <features> > ... > <kvm> > <hidden state='on'/> > </kvm> > </features> > ... > > Signed-off-by: Alex Williamson <alex.williamson(a)redhat.com&gt; > --- > > If it's not obvious, this patch is derived from copying and modifying > the similar hyperv feature support. Hopefully I've found all the > right pieces. > Seems to cover all the bases. couple minor bits: > docs/formatdomain.html.in | 21 ++++ > docs/schemas/domaincommon.rng | 18 +++- > src/conf/domain_conf.c | 100 ++++++++++++++++++++ > src/conf/domain_conf.h | 9 ++ > src/qemu/qemu_command.c | 22 ++++ > tests/qemuargv2xmltest.c | 2 > .../qemuxml2argv-kvm-features-off.args | 5 + > .../qemuxml2argv-kvm-features-off.xml | 27 +++++ > .../qemuxml2argv-kvm-features.args | 5 + > .../qemuxml2argvdata/qemuxml2argv-kvm-features.xml | 27 +++++ > tests/qemuxml2argvtest.c | 3 + > tests/qemuxml2xmltest.c | 3 + > 12 files changed, 240 insertions(+), 2 deletions(-) > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-kvm-features-off.args > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-kvm-features-off.xml > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-kvm-features.args > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-kvm-features.xml > > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in > index bd99ae0..32cc381 100644 > --- a/docs/formatdomain.html.in > +++ b/docs/formatdomain.html.in > @@ -1232,6 +1232,9 @@ > &lt;vapic state='on'/&gt; > &lt;spinlocks state='on' retries='4096'/&gt; > &lt;/hyperv&gt; > + &lt;kvm&gt; > + &lt;hidden state='on'/&gt; > + &lt;/kvm&gt; > &lt;pvspinlock/&gt; > > &lt;/features&gt; > @@ -1310,7 +1313,23 @@ > can be explicitly disabled by using <code>state='off'</code> > attribute. > </dd> > - > + <dt><code>kvm</code></dt> > + <dd>Various features to change the behavior of the KVM hypervisor. > + <table class="top_table"> > + <tr> > + <th>Feature</th> > + <th>Description</th> > + <th>Value</th> > + <th>Since</th> > + </tr> > + <tr> > + <td>hidden</td> > + <td>Hide the KVM hypervisor from standard MSR based discovery</td> > + <td> on, off</td> > + <td><span class="since">2.1.0 (QEMU only)</span></td> > + </tr> > + </table> > + </dd> > </dl> > I'd specify that the default value is 'off' if using KVM, 'on' otherwise, and can be explicitly disabled with 'on'.

> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c > index 8a69976..77a84cc 100644 > --- a/src/qemu/qemu_command.c > +++ b/src/qemu/qemu_command.c > @@ -6228,6 +6228,25 @@ qemuBuildCpuArgStr(virQEMUDriverPtr driver, > } > } > > + if (def->features[VIR_DOMAIN_FEATURE_KVM] == VIR_TRISTATE_SWITCH_ON) { > + if (!have_cpu) { > + virBufferAdd(&buf, default_model, -1); > + have_cpu = true; > + } > + > + for (i = 0; i < VIR_DOMAIN_KVM_LAST; i++) { > + switch ((virDomainKVM) i) { > + case VIR_DOMAIN_KVM_HIDDEN: > + if (def->kvm_features[i] == VIR_TRISTATE_SWITCH_ON) > + virBufferAsprintf(&buf, ",kvm=off"); > + break; > + There's a 'make syntax-check' warning here with latest git: src/qemu/qemu_command.c:6241: virBufferAsprintf(&buf, ",kvm=off"); maint.mk: use virBufferAddLit, not virBufferAsprintf, with a string literal make: *** [sc_prohibit_virBufferAsprintf_with_string_literal] Error 1 The rest looks fine, I'll commit v2 if no one has objections to the XML or code (CCing Peter and Jan who did some of the hyperv work)