Messages in this thread | | | Subject | Re: [PATCH] x86/kvm/hyper-v: Don't deactivate APICv unconditionally when Hyper-V SynIC enabled | From | Paolo Bonzini <> | Date | Fri, 6 Nov 2020 11:18:01 +0100 |
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On 05/11/20 16:53, Vitaly Kuznetsov wrote: >> The current implementation of Hyper-V SynIC[1] request to deactivate >> APICv when SynIC is enabled, since the AutoEOI feature of SynIC is not >> compatible with APICv[2]. >> >> Actually, windows doesn't use AutoEOI if deprecating AutoEOI bit is set >> (CPUID.40000004H:EAX[bit 9], HyperV-TLFS v6.0b section 2.4.5), we don't >> need to disable APICv in this case. >> > Thank you for the patch, the fact that we disable APICv every time we > enable SynIC is nothing to be proud of. I'm, however, not sure we can > treat 'Recommend deprecating AutoEOI' as 'AutoEOI must not be > used.'. Could you please clarify which Windows versions you've tested > with with? >
Indeed---older versions of Windows that predate the deprecation will continue using AutoEOI.
Paolo
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