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Subject: Re: [RFC PATCH v2] Fix: x86: Add missing core serializing
 instruction on migration
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
Reply-To: benh@au1.ibm.com
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Andy Lutomirski <luto@kernel.org>,
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Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
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        Dave Watson <davejwatson@fb.com>, Thomas Gleixner <tglx@linutronix.de>,
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Date: Mon, 13 Nov 2017 10:51:47 +1100
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On Mon, 2017-11-13 at 10:26 +1100, Benjamin Herrenschmidt wrote:
> On Sat, 2017-11-11 at 10:03 -0500, Mathieu Desnoyers wrote:
> > x86 has a missing core serializing instruction in migration scenarios.
> > 
> > Given that x86-32 can return to user-space with sysexit, and x86-64
> > through sysretq and sysretl, which are not core serializing, the
> > following user-space self-modifiying code (JIT) scenario can occur:
> 
> Is this about load/store consistency ? In this case, don't you also
> have problems with get/put_user and not just going to userspace ?

Ah forget it, I saw Linus earlier messages.

Cheers,
Ben.