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=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 63D10C43387 for ; Tue, 18 Dec 2018 05:00:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FA1D217D9 for ; Tue, 18 Dec 2018 05:00:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545109211; bh=AG4tlnMowIVPi36C9DlXqpN0/XcJnQDiuOlazI8YETI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=xOq24S1HLSwkBFYzvJIYzaqm0Zl5jfuQidAZ9M1f+x3NbFDsbtkXiscUep/CPYjba vsE0+3XD7MOv5jM3MSlKWa+myb8tmbZVXBZNKLJtvZB9CIj9aVFm5QLw7eK5NIM3uO rNAttkD6uEMuyvnO5Yw2AGHltz6zbJceH5MRvVwI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726674AbeLRFAK (ORCPT ); Tue, 18 Dec 2018 00:00:10 -0500 Received: from mail.kernel.org ([198.145.29.99]:42636 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726312AbeLRFAJ (ORCPT ); Tue, 18 Dec 2018 00:00:09 -0500 Received: from mail-wm1-f51.google.com (mail-wm1-f51.google.com [209.85.128.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A3B6121841 for ; Tue, 18 Dec 2018 05:00:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545109208; bh=AG4tlnMowIVPi36C9DlXqpN0/XcJnQDiuOlazI8YETI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=OUcPP5USQp1bmXmvNu9gOTZOcqkfXCmO6DjVrRuyL2yd8o2E4D4fkHDVi/oTPSR8e boSqHcInW4ECZqzbz11yqa9KOOp36jnuEPNs5YMfz3EjQo5QIl62NoM8Ol7wArUdre I/SOV43cwzcSCab3SVVL3ark3fMThF69nfSvj1qk= Received: by mail-wm1-f51.google.com with SMTP id m1so1292624wml.2 for ; Mon, 17 Dec 2018 21:00:08 -0800 (PST) X-Gm-Message-State: AA+aEWbHP+5VrSxWLAPfJXU0wMLkdXCpGGzGeuSb5NTGJEZg06RSNMJZ w8m9npxaLmCQJT03eokzoZl4ObxLgRrSNXOcnH+1XQ== X-Google-Smtp-Source: AFSGD/Ww5FWaXGKisvbGt6Ac7HAoRJwKqZyQEkbOFw7ju4a9c1pMszsYmb+UX7hVAEK7w3NQ0iuujy3GP5M9xaeRVKs= X-Received: by 2002:a1c:b1d5:: with SMTP id a204mr1650822wmf.32.1545109205298; Mon, 17 Dec 2018 21:00:05 -0800 (PST) MIME-Version: 1.0 References: <20181116010412.23967-1-jarkko.sakkinen@linux.intel.com> <20181116010412.23967-19-jarkko.sakkinen@linux.intel.com> <7d5cde02-4649-546b-0f03-2d6414bb80b5@intel.com> <20181217180102.GA12560@linux.intel.com> <20181217183613.GD12491@linux.intel.com> <20181217184333.GA26920@linux.intel.com> <20181217222047.GG12491@linux.intel.com> In-Reply-To: <20181217222047.GG12491@linux.intel.com> From: Andy Lutomirski Date: Mon, 17 Dec 2018 20:59:54 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver To: Sean Christopherson Cc: Dave Hansen , Jarkko Sakkinen , X86 ML , Platform Driver , linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, "Ayoun, Serge" , shay.katz-zamir@intel.com, Haitao Huang , Andy Shevchenko , Thomas Gleixner , "Svahn, Kai" , mark.shanahan@intel.com, Suresh Siddha , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Darren Hart , Andy Shevchenko , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 17, 2018 at 2:20 PM Sean Christopherson wrote: > > My brain is still sorting out the details, but I generally like the idea > of allocating an anon inode when creating an enclave, and exposing the > other ioctls() via the returned fd. This is essentially the approach > used by KVM to manage multiple "layers" of ioctls across KVM itself, VMs > and vCPUS. There are even similarities to accessing physical memory via > multiple disparate domains, e.g. host kernel, host userspace and guest. > In my mind, opening /dev/sgx would give you the requisite inode. I'm not 100% sure that the chardev infrastructure allows this, but I think it does. > The only potential hiccup I can see is the build flow. Currently, > EADD+EEXTEND is done via a work queue to avoid major performance issues > (10x regression) when userspace is building multiple enclaves in parallel > using goroutines to wrap Cgo (the issue might apply to any M:N scheduler, > but I've only confirmed the Golang case). The issue is that allocating > an EPC page acts like a blocking syscall when the EPC is under pressure, > i.e. an EPC page isn't immediately available. This causes Go's scheduler > to thrash and tank performance[1]. What's the issue, and how does a workqueue help? I'm wondering if a nicer solution would be an ioctl to add lots of pages in a single call. > > Alternatively, we could change the EADD+EEXTEND flow to not insert the > added page's PFN into the owner's process space, i.e. force userspace to > fault when it runs the enclave. But that only delays the issue because > eventually we'll want to account EPC pages, i.e. add a cgroup, at which > point we'll likely need current->mm anyways. You should be able to account the backing pages to a cgroup without actually sticking them into the EPC, no? Or am I misunderstanding? I guess we'll eventually want a cgroup to limit use of the limited EPC resources.