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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 EE47BC4363D for ; Tue, 22 Sep 2020 18:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77AE623787 for ; Tue, 22 Sep 2020 18:02:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="UgM9Rpk2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726672AbgIVSCS (ORCPT ); Tue, 22 Sep 2020 14:02:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726526AbgIVSCS (ORCPT ); Tue, 22 Sep 2020 14:02:18 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7677C061755; Tue, 22 Sep 2020 11:02:17 -0700 (PDT) Received: from zn.tnic (p200300ec2f0bfb00105f6dfc0f2f9e65.dip0.t-ipconnect.de [IPv6:2003:ec:2f0b:fb00:105f:6dfc:f2f:9e65]) (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 C0E051EC027B; Tue, 22 Sep 2020 20:02:15 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1600797735; 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=9wsNfmarJ+ZwBMwKOM+TIGDi/giemsqRt1pXRwMjD/8=; b=UgM9Rpk2W4r30U2yLEgZ1N7PL8I3ft8uk2H/04npg38QSFeWxbPJUz6CfcFF9pB5ieaL2s NmnNGLh0M4uC9Rso5gHnoS37S13/RcJEmFF3rseBErfi9QlowUApB386aZZcpJYR/r15Ii qDwNj5pRJRzLAUH08TsmAfeSFxQISdA= Date: Tue, 22 Sep 2020 20:02:03 +0200 From: Borislav Petkov To: Sean Christopherson Cc: Jarkko Sakkinen , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jethro Beekman , Jordan Hand , Nathaniel McCallum , Chunyang Hui , Seth Moore , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com Subject: Re: [PATCH v38 16/24] x86/sgx: Add a page reclaimer Message-ID: <20200922180203.GQ22660@zn.tnic> References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> <20200915112842.897265-17-jarkko.sakkinen@linux.intel.com> <20200922104538.GE22660@zn.tnic> <20200922162437.GA30827@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200922162437.GA30827@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Sep 22, 2020 at 09:24:38AM -0700, Sean Christopherson wrote: > The "else if" is correct. Version Array (VA) pages have 512 slots that hold > metadata for evicted EPC pages, i.e. swapping a page out of the EPC requires > a VA slot. For simplicity (LOL), I'll say. > the approach we are taking for initial support is to reserve a VA slot > when adding a page to the enclave[*]. In most cases, reserving a slot > does not require allocating a new VA page, e.g. to reserve slots 1-511 > of the "current" VA page. The if-elif is handling the case where the > current VA page is fully reserved and a new one needs to be allocated. > The if handles the error, the elif handles success, i.e. > > if (IS_ERR(va_page)) <- needed a new VA page, allocation failed > return PTR_ERR(va_page); > else if (va_page) <- needed a new VA page, allocation succeeded > list_add(&va_page->list, &encl->va_pages); > else > <- reused the current VA page Aha, in that case va_page will be NULL but you're not using it in that function later and that current VA page is on encl->va_pages which others can get from there. Ok, gotcha. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette