As explained in QEMU commit 4c257911dcc7c4189768e9651755c849ce9db4e8
intel-pt features should never be included in the CPU models as it was
not supported by KVM back then and even once it started to be supported,
users have to enable it by passing pt_mode=1 parameter to kvm_intel
module. The Icelake-* CPU models with intel-pt included were added to
QEMU 3.1.0 and removed right in the following 4.0.0 release (and even in
3.1.1 maintenance release).
In libvirt 6.10.0 I introduced 'removed' attribute for features included
in our CPU model definitions which we can use to drop intel-pt from
Icelake-* CPU models. Back then I explained we can safely do so only for
features which could never be enabled, which is not the case of intel-pt.
Theoretically, it could be possible to create an environment in which
QEMU would enable intel-pt without asking for it explicitly: it would
need to use a new enough kernel (not available at the time of QEMU
3.1.0) and pt_mode KVM parameter in combination with QEMU 3.1.0 running
a domain with q35 machine type and all that on a CPU which didn't really
exist at that time.
Migrating such domain to a host with newer SW stack including libvirt
with this patch applied would result in incompatible guest ABI (the
virtual CPU would lose intel-pt). However, QEMU changed its CPU models
unconditionally and thus migration would not work even without this
patch. That said, it is safe to follow QEMU and remove the feature from
Icelake-* CPU models in our cpu_map.
https://bugzilla.redhat.com/show_bug.cgi?id=1853972
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Tim Wiederhake <twiederh@redhat.com>
See arch/x86/include/asm/intel-family.h in the Kernel:
#define INTEL_FAM6_ICELAKE_X 0x6A
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@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>
The element specifies whether a particular CPU model can be used when
creating a CPU definition from raw CPUID/MSR data. The @host attribute
determines whether the CPU model can be used (host='on') for creating
CPU definition for host capabilities. Usability of the model for domain
capabilities and host-model CPU definitions is controlled by the @guest
attribute.
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>
