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Subject: Re: [RFC PATCH v2 23/27] mm/mmap: Add IBT bitmap size to address
 space limit check
From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     Dave Hansen <dave.hansen@linux.intel.com>, 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>,
        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>,
        Peter Zijlstra <peterz@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Date:   Wed, 11 Jul 2018 09:56:27 -0700
In-Reply-To: <7cdadb28-a9aa-550b-9e31-30691b64b504@linux.intel.com>
References: <20180710222639.8241-1-yu-cheng.yu@intel.com>
         <20180710222639.8241-24-yu-cheng.yu@intel.com>
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On Tue, 2018-07-10 at 16:57 -0700, Dave Hansen wrote:
> On 07/10/2018 03:26 PM, Yu-cheng Yu wrote:
> > 
> > The indirect branch tracking legacy bitmap takes a large address
> > space.  This causes may_expand_vm() failure on the address limit
> > check.  For a IBT-enabled task, add the bitmap size to the
> > address limit.
> This appears to require that we set up
> current->thread.cet.ibt_bitmap_size _before_ calling may_expand_vm().
> What keeps the ibt_mmap() itself from hitting the address limit?

Yes, that is overlooked.  I will fix it.

Thanks,
Yu-cheng