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 EA347C4363D for ; Mon, 5 Oct 2020 01:31:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B29220759 for ; Mon, 5 Oct 2020 01:31:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="mLsD6Ikb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725909AbgJEBbG (ORCPT ); Sun, 4 Oct 2020 21:31:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725848AbgJEBbF (ORCPT ); Sun, 4 Oct 2020 21:31:05 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76957C0613CE; Sun, 4 Oct 2020 18:31:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0qSk/poAAlh1rgBkhNlRg8Se+ak0sbI4FbkVJHltdr8=; b=mLsD6Ikb8fCqRb4wFjxC2fwp7H 6AZNCciLtFbL3K6A/wkL/KkLBPZy63j6xad5I+eGexCvUSzAawRSWB0tAdmZ7ZjYWVMF3u1f4beLl EbuXu14fMeGwt9DUP7PyljNUqC8MBZec4xbzRZSYz6ZN6GG5dYcqh1bJlJrWFT9cDzBmtFSPtlLJu kIIBNzWc4yqOVkAo8+t3bFu9lVqUhmSdJJ+4WqfNVlVt1NZqh73O8P6aEucOpbm07TzfjFJ9w15hx OCTIdqdw4YvYD+7ySVKJ8qdr7E4U+75LrjQl9Q7jSF/VaWMm5twQhGbPE9SWxKPX6+Og1NAIGU/Az +viEtQWA==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kPFL3-00023F-T2; Mon, 05 Oct 2020 01:30:54 +0000 Date: Mon, 5 Oct 2020 02:30:53 +0100 From: Matthew Wilcox To: Jarkko Sakkinen Cc: x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Jethro Beekman , Haitao Huang , Chunyang Hui , Jordan Hand , Nathaniel McCallum , Seth Moore , Darren Kenny , Sean Christopherson , Suresh Siddha , andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, 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, mikko.ylinen@intel.com Subject: Re: [PATCH v39 11/24] x86/sgx: Add SGX enclave driver Message-ID: <20201005013053.GJ20115@casper.infradead.org> References: <20201003045059.665934-1-jarkko.sakkinen@linux.intel.com> <20201003045059.665934-12-jarkko.sakkinen@linux.intel.com> <20201003195440.GD20115@casper.infradead.org> <20201004215049.GA43926@linux.intel.com> <20201004222750.GI20115@casper.infradead.org> <20201004234153.GA49415@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201004234153.GA49415@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2020 at 02:41:53AM +0300, Jarkko Sakkinen wrote: > On Sun, Oct 04, 2020 at 11:27:50PM +0100, Matthew Wilcox wrote: > > int ret = 0; > > > > mutex_lock(&encl->lock); > > rcu_read_lock(); > > Right, so xa_*() take RCU lock implicitly and xas_* do not. Not necessarily the RCU lock ... I did document all this in xarray.rst: https://www.kernel.org/doc/html/latest/core-api/xarray.html > > while (xas.index < idx_end) { > > page = xas_next(&xas); > > It should iterate through every possible page index within the range, > even the ones that do not have an entry, i.e. this loop also checks > that there are no empty slots. > > Does xas_next() go through every possible index, or skip the non-empty > ones? xas_next(), as its documentation says, will move to the next array index: https://www.kernel.org/doc/html/latest/core-api/xarray.html#c.xas_next > > if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) > > ret = -EACCESS; > > break; > > } > > } > > rcu_read_unlock(); > > mutex_unlock(&encl->lock); > > In my Geminilake NUC the maximum size of the address space is 64GB for > an enclave, and it is not fixed but can grow in microarchitectures > beyond that. > > That means that in (*artificial*) worst case the locks would be kept for > 64*1024*1024*1024/4096 = 16777216 iterations. Oh, there's support for that on the XArray API too. xas_lock_irq(&xas); xas_for_each_marked(&xas, page, end, PAGECACHE_TAG_DIRTY) { xas_set_mark(&xas, PAGECACHE_TAG_TOWRITE); if (++tagged % XA_CHECK_SCHED) continue; xas_pause(&xas); xas_unlock_irq(&xas); cond_resched(); xas_lock_irq(&xas); } xas_unlock_irq(&xas);