While we don't want to aim for the shortest list of disabled features in
the baseline result (it would select a very old model), we want to do so
while looking at any of the input models for which we're trying to
compute a baseline CPU model. Given a set of input models, we always
want to take the least capable one of them (i.e., the one with shortest
list of disabled features) or a better model which is not one of the
input models.
So when considering an input model, we just check whether its list of
disabled features is shorter than the currently best one. When looking
at other models we check both enabled and disabled features while
penalizing disabled features as implemented by the previous patch.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
For finding the best matching CPU model for a given set of features
while we don't know the CPU signature (i.e., when computing a baseline
CPU model) we've been using a "shortest list of features" heuristics.
This works well if new CPU models are supersets of older models, but
that's not always the case. As a result it may actually select a new CPU
model as a baseline while removing some features from it to make it
compatible with older models. This is in general worse than using an old
CPU model with a bunch of added features as a guest OS or apps may crash
when using features that were disabled.
On the other hand we don't want to end up with a very old model which
would guarantee no disabled features as it could stop a guest OS or apps
from using some features provided by the CPU because they would not
expect them on such an old CPU.
This patch changes the heuristics to something in between. Enabled and
disabled features are counted separately so that a CPU model requiring
some features to be disabled looks worse than a model with fewer
disabled features even if its complete list of features is longer. The
penalty given for each additional disabled feature gets bigger to make
longer list of disabled features look even worse.
https://bugzilla.redhat.com/show_bug.cgi?id=1851227
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
These ancient RHEL-only CPU models should not really be used by any CPU
definition created by libvirt. We keep them just for backwards
compatibility with domains which might still be using them.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reporting hv-* properties properly requires hv to be enabled,
see qemu commit 071ce4b03b.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Linux 5.13 introduces "kcpuid", a tool similar to "cpuid", see
https://lore.kernel.org/lkml/1614928878-86075-1-git-send-email-feng.tang@intel.com/
Output formats of cpuid and kcpuid differ slightly. This adds support
for the latter.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
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>
The output of cpuid depends on the logical processor id the process
runs on, as reflected by the "local apic id" present in cpuid leaves
(eax=1,ebx=0), (eax=11,ebx=0), and (eax=11,ebx=1). This produces
arbitrary changes in the output files that complicate comparisons.
This patch masks the occurences of the local apic id with 0x00, so
that two consecutive runs of "./cpu-data.py gather" produce identical
results.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
It is now doing way more than gathering the CPU data from a host as the
other scripts were merged in it.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Due to missing pdpe1gb support in the host CPU data, the CPU is still
incorrectly detected as Westmere-IBRS for host capabilities because we
don't have the option to disable features included in the base model
there.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
It's obvious the CPU model detection provides strange results, which
will be fixed by adding a new Snowridge CPU model few patches later.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
This allows for the functionality of cpu-cpuid.py script to be
integrated more naturally in a later patch.
Changes the way this script should be called:
cpu-gather.py -> cpu-gather.py
cpu-gather.py --gather -> cpu-gather.py gather
cpu-gather.py --parse -> cpu-gather.py parse
cpu-gather.py --gather --parse -> cpu-gather.py full
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Prepare to deduplicate the list of relevant registers for cpuid and
msr information.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Prepare to deduplicate the list of relevant registers for cpuid and
msr information.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
'xmltodict' is a Python module that is not installed by default.
Replace it, so the dependencies of cpu-gather.py do not change
when both scripts are merged.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
'xmltodict' is a Python module that is not installed by default.
Replace it, so the dependencies of cpu-gather.py do not change
when both scripts are merged.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Using 'argparse' for argument handling simplifies merging this script
with cpu-gather.py in a later patch.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Make
./cpu-gather.py --gather --parse
an alias of
./cpu-gather.py [--gather] | ./cpu-gather.py --parse
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
More reliable, easier to parse, easier to edit.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
This changes the invocation from
./cpu-gather.py | ./cpu-parse.sh
to
./cpu-gather.py [--gather] | ./cpu-gather.py --parse
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
This is a preparatory step to replace the output format with
something more readable.
Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
