Oracular will be EOL before this can land, for the rest this LGTM
I've updated SRU template to be more acceptable, hope it is good now.
In -devel I'd like to have the Debian submission done and referenced, then we
can go on.
** Description changed:
[ Impact ]
- libvirt cannot detect all features (e.g. vmx-* features) on recent Intel
- CPUs
+ * libvirt cannot detect all features (e.g. vmx-* features) on recent
+ Intel CPUs
+
+ * The reason is that it tries to read msr content which without the msr
module
+ (or builtin) being loaded will not deliver the right results, leading
+ to mis-detect and mis to use features a CPU would have
+
+ * Load the module at boot and install to overcome that
[ Test Plan ]
On recent Intel CPU (Granite Rapids, Sierra Forest)
$ apt install --yes qemu-system-x86 libvirt-daemon-system libvirt-clients
+ # For the module, should be loaded
+ $ lsmod | grep msr
+ For the actual now better output detecting CPU features in libvirt
$ virsh capabilities
- Some of the vmx-* features are missing in the features list and libvirt
- cannot output the right CPU model name.
+ Some of the vmx-* features are missing in the features list and libvirt
cannot output the right CPU model name. Be aware that capabilities can be
cached,
+ so if you want to also compare with/without loaded module you need to clean
the cache.
+
[ Where problems could occur ]
- The fix only load the msr module at boot, no issue is expected to happen
- elsewhere.
+ The fix only loads the msr module at boot and on install of libvirt.
+ Doing so is a no-op other than the bit of memory usage.
+ No issue is expected to happen elsewhere, if anything then something else
+ that also behaves differently if that is loaded or not, but we'd not be aware
of such a program - and if they insist on not having it loaded it can be
blocked in module configuration.
[ Other Info ]
Recently, some x86 features (vmx-*) are listed as part of the MSR registers
instead of the traditional CPUID instruction.
The MSR is exposed to userspace via device /dev/cpu/*/msr managed by the MSR
kernel module
As of now, this kernel module is not loaded by default on Ubuntu, as a
consequence, libvirt cannot access the MSR registers and is unable to detect
some of the CPU features.
** Changed in: libvirt (Ubuntu Oracular)
Status: Confirmed => Won't Fix
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https://bugs.launchpad.net/bugs/2106791
Title:
Emerald Rapids cannot be used as Sapphire Rapids on Ubuntu due to TSX
features
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