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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 9029BC04AB4 for ; Fri, 17 May 2019 18:33:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5790021726 for ; Fri, 17 May 2019 18:33:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558118033; bh=zBXRbeIQrwFN+otrC2SUsB1tTk/+5ebPtDQk7hrMMvE=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=Eok1hvdo/YtXNqT7JebhwPcdwsBrOfWJa1sGUUrpAI27yDYemOJOstSHjwLOkE0AA cpv/tRaK9VCXGF4ZtR0MFxA5hTAV5+FcNzm1hVmefmwsOMjAX92t0sF7dD+9beX7LF E/pvm03wORyeu6a4af1pxVcx2+T475Tc1ASnirmk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727001AbfEQSdw (ORCPT ); Fri, 17 May 2019 14:33:52 -0400 Received: from mail-lf1-f66.google.com ([209.85.167.66]:41403 "EHLO mail-lf1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726282AbfEQSdw (ORCPT ); Fri, 17 May 2019 14:33:52 -0400 Received: by mail-lf1-f66.google.com with SMTP id d8so6004152lfb.8 for ; Fri, 17 May 2019 11:33:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=oO/GMUgT+1j7VBkn8MyV9uRSDi94nW1hm071Hw5jVSo=; b=Fg3ijOgmH36WIunWDge4wgVr1HpSUVX9oAp+UCHPw0NDKT8DXkwZR5Mut0XUVphKdk 7WE868HzNhOuKCXNTdn21kpMbzVCMJsRd2eClEQCb4geolrkgNdveLxZ1t0pqQciLaT5 bwxxuYpv6Ki2BW9/dHBX6rwlLrcuW+6kpcRCs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=oO/GMUgT+1j7VBkn8MyV9uRSDi94nW1hm071Hw5jVSo=; b=cm/Q2FH4JqMyIzeIsajsfceHPuIfiYhnBNlsuB6EFU2OS135LCNIhDmEgvq02LXGcK gyXSreipT36S206xE3Q0FefqbgeQwtLLilg2ef0DKeq2xKTGN3lVfyKStZ11Cezy6YTh 4HvpxjjplTrZn4rNl5RMzsLFhJstmaoxOZKbAFYPnjltA7LNmvo9vl+GPFM/le7cxWwc WTzUaXbipSsrjPT5lfYalUuiy234YDWOVIhCrk8fBy60iFryJTjq/PNF4VrNnVZmRi01 mP5PVSo6YWseBvbz/eLsjP/MOlD0xh3AMepopEgBWOTgMUexD/XTH7wDBzgyF2Og6brQ bXvg== X-Gm-Message-State: APjAAAVMWcbIMXeu60nu2xsLpaA9wcItFz2CFe9fbD6t6BHGJ2vlwpO5 vqsnou+W5jE3ti8OfyfIW5j54jqaUk8= X-Google-Smtp-Source: APXvYqw0Q8wjIuUdRQC6oDQV01saSviPC/Z6q7W2LOglH1xaEujSrG4wMAFgyZ4tQtcFFsR6Gv843w== X-Received: by 2002:ac2:510b:: with SMTP id q11mr26721593lfb.11.1558118029440; Fri, 17 May 2019 11:33:49 -0700 (PDT) Received: from mail-lj1-f171.google.com (mail-lj1-f171.google.com. [209.85.208.171]) by smtp.gmail.com with ESMTPSA id v24sm1696174lje.25.2019.05.17.11.33.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 17 May 2019 11:33:46 -0700 (PDT) Received: by mail-lj1-f171.google.com with SMTP id d15so7138547ljc.7 for ; Fri, 17 May 2019 11:33:46 -0700 (PDT) X-Received: by 2002:a2e:9546:: with SMTP id t6mr8446776ljh.51.1558118026162; Fri, 17 May 2019 11:33:46 -0700 (PDT) MIME-Version: 1.0 References: <960B34DE67B9E140824F1DCDEC400C0F654E3FB9@ORSMSX116.amr.corp.intel.com> <6a97c099-2f42-672e-a258-95bc09152363@tycho.nsa.gov> <20190517150948.GA15632@linux.intel.com> <80013cca-f1c2-f4d5-7558-8f4e752ada76@tycho.nsa.gov> <20190517172953.GC15006@linux.intel.com> <20190517175500.GE15006@linux.intel.com> <20190517182124.GF15006@linux.intel.com> In-Reply-To: <20190517182124.GF15006@linux.intel.com> From: Linus Torvalds Date: Fri, 17 May 2019 11:33:30 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support) To: Sean Christopherson Cc: Andy Lutomirski , Stephen Smalley , "Xing, Cedric" , Andy Lutomirski , James Morris , "Serge E. Hallyn" , LSM List , Paul Moore , Eric Paris , "selinux@vger.kernel.org" , Jarkko Sakkinen , Jethro Beekman , "Hansen, Dave" , Thomas Gleixner , "Dr. Greg" , 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 Content-Type: text/plain; charset="UTF-8" Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Fri, May 17, 2019 at 11:21 AM Sean Christopherson wrote: > > I agree that conceptually EPC is private memory, but because EPC is > managed as a separate memory pool, SGX tags it VM_PFNMAP and manually > inserts PFNs, i.e. EPC effectively it gets classified as IO memory. > > And vmf_insert_pfn_prot() doesn't like writable private IO mappings: > > BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); Hmm. I haven't looked into why you want to do your own page insertion and not just "use existing pages", but I'm sure there's some reason. It looks like the "shared vs private" inode part is a red herring, though. You might as well give each opener of the sgx node its own inode - and you probably should. Then you can keep track of the pages that have been added in the inode->i_mapping, and you could avoid the whole PFN thing entirely. I still am not a huge fan of the device node in the first place, but I guess it's just one more place where a system admin can then give (or deny) access to a kernel feature from users. I guess the kvm people do the same thing, for not necessarily any better reasons. With the PFNMAP model I guess the SGX memory ends up being unswappable - at least done the obvious way. Again, the way I'd expect it to be done is as a shmem inode - that would I think be a better model. But I think that's a largely internal design decision, and the device node could just do that eventually (and the mmap could just map the populated shmem information into memory, no PFNMAP needed - the inode and the mapping could be "read-only" as far as the _user_ is concerned, but the i_mapping then gets populated by the ioctl's). I have not actually looked at any of the SGX patches, so maybe you're already doing something like that (although the PFNMAP comment makes me think not), and quite possibly there's some fundamental reason why you can't just use the shmem approach. So my high-level reaction here may be just the rantings of somebody who just isn't familiar with what you do. My "why not shmem and regular mmap" questions come from a 30000ft view without knowing any of the details. Linus