linux-kernel - Re: [PATCH] x86/hyper-v: implement EOI assist

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Message-ID: <87v9zfh2rr.fsf@vitty.brq.redhat.com>
Date:   Mon, 15 Apr 2019 14:27:36 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Long Li <longli@...rosoft.com>, Simon Xiao <sixiao@...rosoft.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@...rosoft.com>,
        linux-hyperv@...r.kernel.org
Subject: Re: [PATCH] x86/hyper-v: implement EOI assist

Vitaly Kuznetsov <vkuznets@...hat.com> writes:

> Hyper-V TLFS suggests an optimization to avoid imminent VMExit on EOI:
> "The OS performs an EOI by atomically writing zero to the EOI Assist field
> of the virtual VP assist page and checking whether the "No EOI required"
> field was previously zero. If it was, the OS must write to the
> HV_X64_APIC_EOI MSR thereby triggering an intercept into the hypervisor."
>
> Implement the optimization in Linux.
>

Simon, Long,

did you get a chance to run some tests with this?

-- 
Vitaly