From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>, junjiehua0xff@gmail.com
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Andrey Smetanin <asmetanin@virtuozzo.com>,
Junjie Hua <junjiehua@tencent.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/kvm/hyper-v: Don't deactivate APICv unconditionally when Hyper-V SynIC enabled
Date: Fri, 6 Nov 2020 11:18:01 +0100 [thread overview]
Message-ID: <348f8763-3842-0dda-2c01-6c5d510fe630@redhat.com> (raw)
In-Reply-To: <87sg9n3ilt.fsf@vitty.brq.redhat.com>
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
prev parent reply other threads:[~2020-11-06 10:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-05 9:12 junjiehua0xff
2020-11-05 15:53 ` Vitaly Kuznetsov
2020-11-06 10:18 ` Paolo Bonzini [this message]
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