Hi Vitaly, On Tue, Mar 05, 2024 at 05:42:04PM +0100, Vitaly Kuznetsov wrote: > Date: Tue, 5 Mar 2024 17:42:04 +0100 > From: Vitaly Kuznetsov <vkuzn...@redhat.com> > Subject: [PATCH RESEND v3 3/3] docs/system: Add recommendations to Hyper-V > enlightenments doc > > While hyperv.rst already has all currently implemented Hyper-V > enlightenments documented, it may be unclear what is the recommended set to > achieve the best result. Add the corresponding section to the doc. > > Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com> > --- > docs/system/i386/hyperv.rst | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst > index 009947e39141..1c1de77feb65 100644 > --- a/docs/system/i386/hyperv.rst > +++ b/docs/system/i386/hyperv.rst > @@ -283,6 +283,36 @@ Supplementary features > feature alters this behavior and only allows the guest to use exposed > Hyper-V > enlightenments. > > +Recommendations > +---------------
This guide is very helpful! > +To achieve the best performance of Windows and Hyper-V guests and unless > there > +are any specific requirements (e.g. migration to older QEMU/KVM versions, > +emulating specific Hyper-V version, ...), it is recommended to enable all > +currently implemented Hyper-V enlightenments with the following exceptions: > + > +- ``hv-syndbg``, ``hv-passthrough``, ``hv-enforce-cpuid`` should not be > enabled > + in production configurations as these are debugging/development features. > +- ``hv-reset`` can be avoided as modern Hyper-V versions don't expose it. Does the "Hyper-V versions" means Hyper-V guest version or Microsoft's Hyper-V hypervisor version? It would be better to clarify Hyper-V guest and Hyper-v hypervisor. And it would be better to have a clear version number. > +- ``hv-evmcs`` can (and should) be enabled on Intel CPUs only. While the > feature > + is only used in nested configurations (Hyper-V, WSL2), enabling it for > regular > + Windows guests should not have any negative effects. > +- ``hv-no-nonarch-coresharing`` must only be enabled if vCPUs are properly > pinned > + so no non-architectural core sharing is possible. > +- ``hv-vendor-id``, ``hv-version-id-build``, ``hv-version-id-major``, > + ``hv-version-id-minor``, ``hv-version-id-spack``, > ``hv-version-id-sbranch``, > + ``hv-version-id-snumber`` can be left unchanged, guests are not supposed to > + behave differently when different Hyper-V version is presented to them. > +- ``hv-crash`` must only be enabled if the crash information is consumed via > + QAPI by higher levels of the virtualization stack. Enabling this feature > + effectively prevents Windows from creating dumps upon crashes. > +- ``hv-reenlightenment`` can only be used on hardware which supports TSC > + scaling or when guest migration is not needed. > +- ``hv-spinlocks`` should be set to e.g. 0xfff when host CPUs are > overcommited > + (meaning there are other scheduled tasks or guests) and can be left > unchanged > + from the default value (0xffffffff) otherwise. > +- ``hv-avic``/``hv-apicv`` should not be enabled if the hardware does not > + support APIC virtualization (Intel APICv, AMD AVIC). > It's also better to add blank lines between paragraphs above. BTW, may I ask another Windows question? I understand that Windows such as Windows 10 and later is already a virtualized architecture with built-in Hyper-V to run root partation. So is it true that booting Windows VM via KVM + QEMU is running Windows Guest in L2? Or what is the relationship between Hyper-V within Windows and Hyper-V enlightenments with QEMU + KVM? Thanks, Zhao
