From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02D27C31E4D for ; Fri, 14 Jun 2019 15:18:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D97B22168B for ; Fri, 14 Jun 2019 15:18:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725923AbfFNPSk (ORCPT ); Fri, 14 Jun 2019 11:18:40 -0400 Received: from mga18.intel.com ([134.134.136.126]:63789 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725851AbfFNPSk (ORCPT ); Fri, 14 Jun 2019 11:18:40 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jun 2019 08:18:39 -0700 X-ExtLoop1: 1 Received: from mdumitrx-mobl1.ger.corp.intel.com (HELO localhost) ([10.249.32.245]) by orsmga005.jf.intel.com with ESMTP; 14 Jun 2019 08:18:29 -0700 Date: Fri, 14 Jun 2019 18:18:28 +0300 From: Jarkko Sakkinen To: Sean Christopherson Cc: "Xing, Cedric" , Andy Lutomirski , Andy Lutomirski , Stephen Smalley , James Morris , "Serge E . Hallyn" , LSM List , Paul Moore , Eric Paris , "selinux@vger.kernel.org" , Jethro Beekman , "Hansen, Dave" , Thomas Gleixner , Linus Torvalds , LKML , X86 ML , "linux-sgx@vger.kernel.org" , Andrew Morton , "nhorman@redhat.com" , "npmccallum@redhat.com" , "Ayoun, Serge" , "Katz-zamir, Shay" , "Huang, Haitao" , Andy Shevchenko , "Svahn, Kai" , Borislav Petkov , Josh Triplett , "Huang, Kai" , David Rientjes , "Roberts, William C" , "Tricca, Philip B" Subject: Re: [RFC PATCH 2/9] x86/sgx: Do not naturally align MAP_FIXED address Message-ID: <20190614151805.GB11241@linux.intel.com> References: <20190531233159.30992-3-sean.j.christopherson@intel.com> <20190604114951.GC30594@linux.intel.com> <960B34DE67B9E140824F1DCDEC400C0F654EDBDE@ORSMSX116.amr.corp.intel.com> <20190605151653.GK11331@linux.intel.com> <5A85C1D7-A159-437E-B42A-3F4254E07305@amacapital.net> <20190606153710.GB25112@linux.intel.com> <20190613134800.GA12791@linux.intel.com> <960B34DE67B9E140824F1DCDEC400C0F65503A93@ORSMSX116.amr.corp.intel.com> <20190613171451.GD5850@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190613171451.GD5850@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org On Thu, Jun 13, 2019 at 10:14:51AM -0700, Sean Christopherson wrote: > > I don't get this. The swapper takes a read lock on mm->mmap_sem, which locks > > the vma, which in turn reference counts vma->vm_file. Why is the internal > > refcount still needed? > > mmap_sem is only held when reclaim is touching PTEs, e.g. to test/clear > its accessed bit and to zap the PTE. The liveliness of the enclave needs > to be guaranteed for the entire duration of reclaim, e.g. we can't have > the enclave disappearing when we go to do EWB. It's also worth nothing > that a single reclaim may operate on more than one mmap_sem, as enclaves > can be shared across processes (mm_structs). Anyway, the takeaway I got from this is that encl->refcount does not need to be updated for VMAs (sent a patch to linux-sgx that I plan merge). /Jarkko