2:30 p.m.
Hi all,
lately I've been involved again in hyperv support. I was tasked to help
improve the testability of the hyperv guest configuration.
Hyperv support is a set of optimizations that libvirt/qemu offer to
improve the runtime behaviour (stability, performance) of Windows guets.
See for example: https://libvirt.org/formatdomain.html#elementsFeatures
oVirt does support them (see for example
https://github.com/oVirt/vdsm/blob/master/lib/vdsm/virt/libvirtxml.py#L243)
and will keep supporting them
because they are a key feature for windows guests.
Up until now the easiest (only?) way to check if a hyperv optmization
was really enabled was to inspect the libvirt XML and/or the QEMU
command line flags
But we wanted to have another check.
Enter hvinfo: https://github.com/fromanirh/hvinfo
hvinfo is a simple tool that decodes CPUID informations according to the
publicly-available HyperV specs
(https://github.com/MicrosoftDocs/Virtualization-Documentation/tree/live/tlfs)
and report what the guest sees.
It takes no arguments - just run it!-, it requires no special privileges
and emits easy to consume JSON. It is designed to help and integrate
into fully automated CI/QA.
Being a commandline tool, is hard to give a "screenshot", so let me just
report sample output (admin privileges not actually required)
Windows PowerShell
Copyright (C) Microsoft Corporation. All rights reserved.
PS C:\Users\admin> cd .\Downloads\
PS C:\Users\admin\Downloads> .\hvinfo.exe
{
"HyperVsupport": true,
"Features": {
"GuestDebugging": false,
"PerformanceMonitor": false,
"PCPUDynamicPartitioningEvents": true,
"HypercallInputParamsXMM": false,
"VirtualGuestIdleState": false,
"HypervisorSleepState": false,
"NUMADistanceQuery": false,
"TimerFrequenciesQuery": false,
"SytheticMCEInjection": false,
"GuestCrashMSR": false,
"DebugMSR": false,
"NPIEP": false,
"DisableHypervisorAvailable": false,
"ExtendedGvaRangesForFlushVirtualAddressList": false,
"HypercallOutputReturnXMM": false,
"SintPollingMode": false,
"HypercallMsrLock": false,
"UseDirectSyntheticTimers": false
},
"Recommendations": {
"HypercallAddressSpaceSwitch": false,
"HypercallLocalTLBFlush": false,
"HypercallRemoteTLBFlush": false,
"MSRAPICRegisters": true,
"MSRSystemReset": false,
"RelaxedTiming": true,
"DMARemapping": false,
"InterruptRemapping": false,
"X2APICMSR": false,
"DeprecatingAutoEOI": false,
"SyntheticClusterIPI": false,
"ExProcessorMasks": false,
"Nested": false,
"INTForMBECSyscalls": false,
"NestedEVMCS": false,
"SyncedTimeline": false,
"DirectLocalFlushEntire": false,
"NoNonArchitecturalCoreSharing": false,
"SpinlockRetries": 8191
}
}
PS C:\Users\admin\Downloads>
Caveat: the name of the features are the same of the spec, so we need
mappings for oVirt flags, libvirt flags and so on.
For example
libvirt xml
domain.features.hyperv.relaxed[state="on"]
maps to hvinfo json
Features.Recommendations.RelaxedTiming=true
Feel free to test it and report any issue
Bests,
--
Francesco Romani
Senior SW Eng., Virtualization R&D
Red Hat
IRC: fromani github: @fromanirh