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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 1213BC433E0 for ; Wed, 27 May 2020 20:35:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E727E20835 for ; Wed, 27 May 2020 20:35:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="VY75sItQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728639AbgE0UfU (ORCPT ); Wed, 27 May 2020 16:35:20 -0400 Received: from mail.skyhub.de ([5.9.137.197]:50190 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727863AbgE0UfT (ORCPT ); Wed, 27 May 2020 16:35:19 -0400 Received: from zn.tnic (p200300ec2f0b8700952f735680ed3731.dip0.t-ipconnect.de [IPv6:2003:ec:2f0b:8700:952f:7356:80ed:3731]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 1776C1EC03C1; Wed, 27 May 2020 22:35:18 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1590611718; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=Fep83zRm+Nc7tQ6A7zu8+T4rH0ND8Zz8ls3kfkFk4SI=; b=VY75sItQDw1a1hMKOoFW96sfa0194tgCd1e9izbox020MO80E8JMS8k5gbvW7b7dssu+mb M+BUSh583sbLWJUTCRvLtzeYoaLl8rt9v3QBeimFM2JUQ+tx8QbFBDWIXEc5CS39edaVq4 qA7P188tgPOAc3ejBmjTn92VGlUUAlA= Date: Wed, 27 May 2020 22:35:09 +0200 From: Borislav Petkov To: Sean Christopherson Cc: Jarkko Sakkinen , linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org, akpm@linux-foundation.org, dave.hansen@intel.com, nhorman@redhat.com, npmccallum@redhat.com, haitao.huang@intel.com, andriy.shevchenko@linux.intel.com, tglx@linutronix.de, kai.svahn@intel.com, josh@joshtriplett.org, luto@kernel.org, kai.huang@intel.com, rientjes@google.com, cedric.xing@intel.com, puiterwijk@redhat.com, Serge Ayoun , Jethro Beekman Subject: Re: [PATCH v30 07/20] x86/sgx: Enumerate and track EPC sections Message-ID: <20200527203509.GF1721@zn.tnic> References: <20200515004410.723949-1-jarkko.sakkinen@linux.intel.com> <20200515004410.723949-8-jarkko.sakkinen@linux.intel.com> <20200525092304.GD25636@zn.tnic> <20200527035613.GH31696@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200527035613.GH31696@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 26, 2020 at 08:56:14PM -0700, Sean Christopherson wrote: > > > + if (i == ARRAY_SIZE(sgx_epc_sections)) { > > > + pr_warn("No free slot for an EPC section\n"); > > > + break; > > > + } > > > > This is also the loop termination: do we really need this warn or can > > the loop simply do "i < ARRAY_SIZE" ? > > The warn alerts the user that there will effectively be lost/unused memory, > so IMO it's worth keeping. Can the user do anything about it? If not, then probably no need to say anything. > > > + pr_info("EPC section 0x%llx-0x%llx\n", pa, pa + size - 1); > > > > I'm assuming that's useful information to issue in dmesg? > > Yes, it's effectively the equivalent of dumping the e820 tables. It might > not be as useful now that the code is stable, but I suspect it will come in > handy for debug/triage down the road. Ok. > > Same for this one: also shared only among sgx code? > > Yes, that one can definitely be buried behind a helper. Shared only within sgx is fine. > One idea would be to provide a Kconfig a la NR_CPUS or NODES_SHIFT. I.e. > carve out the bits in sgx_epc_page_desc to allow up to N sections, but let > the user limit the number of sections to recoup the unused memory. I'd prefer a good estimate of a highest value, say 8 bits, which should suffice for the foreseeable future. That's the simplest thing to do and our Kconfig symbols space is an abomination of gazillion symbols. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette