linux-kernel - RE: [PATCH] x86/hyper-v: Zero out the VP assist page to fix CPU offlining

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Message-ID: <alpine.DEB.2.21.1907180955130.1778@nanos.tec.linutronix.de>
Date:   Thu, 18 Jul 2019 09:56:16 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dexuan Cui <decui@...rosoft.com>
cc:     Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Long Li <longli@...rosoft.com>, vkuznets <vkuznets@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH] x86/hyper-v: Zero out the VP assist page to fix CPU
 offlining

On Thu, 18 Jul 2019, Dexuan Cui wrote:
> 
> The concept of the "overlay page" seems weird, and frankly speaking, 
> I don't really understand why the Hyper-V guys invented it, but as far
> as this patch here is concerned, I think the patch is safe and it can
> indeed fix the CPU offlining issue I described.

Then this needs some really good explanation and in the change log because
that's really obscure behaviour.

Thanks,

	tglx