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Date: Fri, 8 Sep 2017 09:57:26 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: "Thomas Gleixner" <tglx@linutronix.de>
Cc: "LKML" <linux-kernel@vger.kernel.org>,
        "Stephen Hemminger" <sthemmin@microsoft.com>,
        "Simon Xiao" <sixiao@microsoft.com>,
        "KY Srinivasan" <kys@microsoft.com>,
        "Haiyang Zhang" <haiyangz@microsoft.com>,
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        "Peter Zijlstra" <peterz@infradead.org>,
        "Linus Torvalds" <torvalds@linux-foundation.org>,
        "Josh Poimboeuf" <jpoimboe@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Denys Vlasenko" <dvlasenk@redhat.com>,
        "Brian Gerst" <brgerst@gmail.com>, "Borislav Petkov" <bp@alien8.de>,
        "Andy Lutomirski" <luto@kernel.org>
Subject: Re: [PATCH] x86/idt: Unbreak MS HyperV hypercall vector install
Message-ID: <20170908095726.35b82463@xeon-e3>
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On Fri, 8 Sep 2017 01:19:52 -0700
"Thomas Gleixner" <tglx@linutronix.de> wrote:

> The rework of the IDT setup changed the way how unused system gates are
> accounted. At the end of the gate initialization all unused gates in the
> system vector area are set to the spurios handler and marked as used for
> consistency reasons.
> 
> Marking them as used breaks MS HyperV because it installs its hypercall
> vector after that point and the installation is guarded by the bit in the
> used_vectors map. So the hyperv vector stays directed to the spurious
> interrupt handler.
> 
> Leave them marked as unused again and unbreak HyperV that way.
> 
> Fixes: dc20b2d52653 ("x86/idt: Move interrupt gate initialization to IDT
> code")
> Reported-by: Stephen Hemminger <sthemmin@microsoft.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

This fixes it, thanks.

Tested-by: Stephen Hemminger <sthemmin@microsoft.com>