The mpx feature was removed from the corresponding qemu cpu models.
With mpx in the libvirt cpu models, libvirt believes the feature
to be implicitly enabled when creating qemu VMs, while in fact it is
disabled.
This became an issue when commit 94eacd5a5f introduced new vmx-*
features, of which some are dependent on mpx (see "feature_dependencies"
table in qemu target/i386/cpu.c), e.g. vmx-exit-clear-bndcfgs and
vmx-entry-load-bndcfgs. These features cannot be enabled by qemu
without also mpx being enabled, leading to the error message
error: Failed to create domain from testdomain.xml
error: operation failed: guest CPU doesn't match
specification: missing features: mpx,vmx-exit-clear-bndcfgs,
vmx-entry-load-bndcfgs
when trying to create a VM with a "host-model" cpu on a host that
does support mpx and the mentioned vmx-* features:
<domain>
...
<cpu mode='host-model' check='full' />
...
</domain>
Resolve the issue by removing mpx from libvirt's cpu models as well.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Host-model CPU definitions (and domain capabilities) will use the
original CPU models (without noTSX in their name) and explicitly disable
hle and rtm features. This way domains with host-model CPUs will be
migratable even to older versions of libvirt which do not support the
noTSX model variants.
The new models will be advertised in host capabilities and they may
be used explicitly with custom CPUs.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
One of the mitigation methods for TAA[1] is to disable TSX
support on the host system. Linux added a mechanism to disable
TSX globally through the kernel command line, and many Linux
distributions now default to tsx=off. This makes existing CPU
models that have HLE and RTM enabled not usable anymore.
Add new versions of all CPU models that have the HLE and RTM
features enabled, that can be used when TSX is disabled in the
host system.
On systems disabling the features without those types defined
in cpu-maps users end up without modern CPU types in the list
of usable CPUs to use in the likes of virsh domcapabilities
or tools higher in the stack like virt-manager.
This adds:
-Cascadelake-Server-noTSX
-Icelake-Client-noTSX
-Icelake-Server-noTSX
-Skylake-Server-noTSX-IBRS
-Skylake-Client-noTSX-IBRS
Introduced in QEMU by commit v4.2.0-rc2-3-g9ab2237f19 (function)
and commit v4.2.0-rc2-4-g02fa60d101 (names)
References:
[1] TAA, TSX asynchronous Abort:
https://software.intel.com/security-software-guidance/insights/deep-dive-intel-transactional-synchronization-extensions-intel-tsx-asynchronous-aborthttps://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html
Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1853200
Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Message-Id: <20200310104806.2723-2-christian.ehrhardt@canonical.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
