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Date:   Wed, 5 Jun 2019 07:08:15 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     "Xing, Cedric" <cedric.xing@intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        LSM List <linux-security-module@vger.kernel.org>,
        Paul Moore <paul@paul-moore.com>,
        Eric Paris <eparis@parisplace.org>,
        "selinux@vger.kernel.org" <selinux@vger.kernel.org>,
        Jethro Beekman <jethro@fortanix.com>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        "Svahn, Kai" <kai.svahn@intel.com>, Borislav Petkov <bp@alien8.de>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        David Rientjes <rientjes@google.com>,
        "Roberts, William C" <william.c.roberts@intel.com>,
        "Tricca, Philip B" <philip.b.tricca@intel.com>
Subject: Re: [RFC PATCH 2/9] x86/sgx: Do not naturally align MAP_FIXED address
Message-ID: <20190605140815.GA26328@linux.intel.com>
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On Tue, Jun 04, 2019 at 03:10:22PM -0700, Xing, Cedric wrote:
> A bit off topic here. This mmap()/mprotect() discussion reminds me a question
> (guess for Jarkko): Now that vma->vm_file->private_data keeps a pointer to
> the enclave, why do we store it again in vma->vm_private? It isn't a big deal
> but non-NULL vm_private does prevent mprotect() from merging adjacent VMAs. 

vma->vm_ops->close also prevents merging, and we need that to refcount the
enclave and mm.

We also rely on nullifying vma->vm_private_data in the unlikely event that
adding a new mm to the enclave fails on kzalloc().