linux-kernel - Re: [PATCH v4] KVM: VMX: Enable MSR-BASED TPR shadow even if APICv is inactive

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Message-ID: <20160922231350.GB7554@potion>
Date:   Fri, 23 Sep 2016 01:13:50 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wincy Van <fanwenyi0529@...il.com>,
        Yang Zhang <yang.zhang.wz@...il.com>
Subject: Re: [PATCH v4] KVM: VMX: Enable MSR-BASED TPR shadow even if APICv
 is inactive

2016-09-22 07:43+0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@...mail.com>
> 
> I observed that kvmvapic(to optimize flexpriority=N or AMD) is used 
> to boost TPR access when testing kvm-unit-test/eventinj.flat tpr case
> on my haswell desktop (w/ flexpriority, w/o APICv). Commit (8d14695f9542 
> x86, apicv: add virtual x2apic support) disable virtual x2apic mode 
> completely if w/o APICv, and the author also told me that windows guest
> can't enter into x2apic mode when he developed the APICv feature several 
> years ago. However, it is not truth currently, Interrupt Remapping and 
> vIOMMU is added to qemu and the developers from Intel test windows 8 can 
> work in x2apic mode w/ Interrupt Remapping enabled recently. 
> 
> This patch enables TPR shadow for virtual x2apic mode to boost 
> windows guest in x2apic mode even if w/o APICv.
> 
> Can pass the kvm-unit-test.
> 
> Suggested-by: Radim Krčmář <rkrcmar@...hat.com>
> Suggested-by: Wincy Van <fanwenyi0529@...il.com>
> Reviewed-by: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Wincy Van <fanwenyi0529@...il.com>
> Cc: Yang Zhang <yang.zhang.wz@...il.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---

Applied to kvm/queue, thanks.