linux-kernel - Re: [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush

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Message-ID: <20170811125442.5nyrvcylhdrmryt2@hirez.programming.kicks-ass.net>
Date:   Fri, 11 Aug 2017 14:54:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jork Loeser <Jork.Loeser@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Simon Xiao <sixiao@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>, boris.ostrovsky@...cle.com,
        xen-devel@...ts.xenproject.org
Subject: Re: [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB
 flush

On Fri, Aug 11, 2017 at 02:46:41PM +0200, Juergen Gross wrote:
> Aah, okay. Now I understand the problem. The TLB isn't the issue but the
> IPI is serving two purposes here: TLB flushing (which is allowed to
> happen at any time) and serialization regarding access to critical pages
> (which seems to be broken in the Xen case as you suggest).

Indeed, and now hyper-v as well.