linux-kernel - RE: [PATCH] x86/idt: Unbreak MS HyperV hypercall vector install

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Message-ID: <MWHPR21MB0479B3BDFE71A58B11E42165CA950@MWHPR21MB0479.namprd21.prod.outlook.com>
Date:   Fri, 8 Sep 2017 16:12:42 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     Stephen Hemminger <sthemmin@...rosoft.com>,
        Simon Xiao <sixiao@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "Brian Gerst" <brgerst@...il.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: RE: [PATCH] x86/idt: Unbreak MS HyperV hypercall vector install



> -----Original Message-----
> From: Thomas Gleixner [mailto:tglx@...utronix.de]
> Sent: Friday, September 8, 2017 4:20 AM
> To: LKML <linux-kernel@...r.kernel.org>
> Cc: Stephen Hemminger <sthemmin@...rosoft.com>; Simon Xiao
> <sixiao@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Steven Rostedt <rostedt@...dmis.org>; Peter
> Zijlstra <peterz@...radead.org>; Linus Torvalds <torvalds@...ux-
> foundation.org>; Josh Poimboeuf <jpoimboe@...hat.com>; H. Peter Anvin
> <hpa@...or.com>; Denys Vlasenko <dvlasenk@...hat.com>; Brian Gerst
> <brgerst@...il.com>; Borislav Petkov <bp@...en8.de>; Andy Lutomirski
> <luto@...nel.org>
> Subject: [PATCH] x86/idt: Unbreak MS HyperV hypercall vector install
> 
> 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@...rosoft.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Thanks for the quick response.
I tested the patch and the kernel boots up on Hyper-V now.

Reviewed-and-Tested-by: Haiyang Zhang <haiyangz@...rosoft.com>