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Message-ID: <1531325701.13297.32.camel@intel.com>
Subject: Re: [RFC PATCH v2 08/27] mm: Introduce VM_SHSTK for shadow stack
 memory
From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@amacapital.net>,
        Balbir Singh <bsingharora@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromiun.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Date:   Wed, 11 Jul 2018 09:15:01 -0700
In-Reply-To: <20180711083412.GP2476@hirez.programming.kicks-ass.net>
References: <20180710222639.8241-1-yu-cheng.yu@intel.com>
         <20180710222639.8241-9-yu-cheng.yu@intel.com>
         <20180711083412.GP2476@hirez.programming.kicks-ass.net>
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On Wed, 2018-07-11 at 10:34 +0200, Peter Zijlstra wrote:
> On Tue, Jul 10, 2018 at 03:26:20PM -0700, Yu-cheng Yu wrote:
> > 
> > VM_SHSTK indicates a shadow stack memory area.
> > 
> > A shadow stack PTE must be read-only and dirty.  For non shadow
> > stack, we use a spare bit of the 64-bit PTE for dirty.  The PTE
> > changes are in the next patch.
> This doesn't make any sense.. the $subject and the patch seem
> completely
> unrelated to this Changelog.

I was trying to say why this is only defined for 64-bit.  I will fix
it.

Yu-cheng