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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 101D4C433F5 for ; Wed, 9 Mar 2022 08:02:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229765AbiCIIDJ (ORCPT ); Wed, 9 Mar 2022 03:03:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231331AbiCIIDC (ORCPT ); Wed, 9 Mar 2022 03:03:02 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F45314CC97; Wed, 9 Mar 2022 00:02:04 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0792EB81EA0; Wed, 9 Mar 2022 08:02:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A102C340E8; Wed, 9 Mar 2022 08:02:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646812921; bh=Cfr19P9SP1R7zJ9J1a4BDOPpbOGBYdEhzLA2WG9WWJ0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=isNV1LXjqaCsYQBMI6d599yCQUTKjNX37a/8sc2iAFHN5pNR0NL/RrsEgRPeLsiit 9D40wPq76w4owzq/8nK6bmcyY8woCl02YeKNNrvYZQrqKQ/hdJYnfWant+LdvnX31F T2VBiMwCFaN7saoRuAcYM6HSQws04TUwJccPzEm/N0LdRHs0usa9mZ56fWB4qQLyH0 j5jgLnTzrxvxbBxJ4Rln9iBEcVaZQtAQTXce4YH7GN/xXpq3aLv27dFHSYaWAh5zuG OTNhJjgN6O51RBOlk9KbOHVAWLAl16qDD9NcLAqKjoTBalSR3yG15fJj+Eil3iU5n/ Huud267loJ3EQ== Date: Wed, 9 Mar 2022 10:01:17 +0200 From: Jarkko Sakkinen To: Reinette Chatre Cc: linux-sgx@vger.kernel.org, Dave Hansen , stable@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , Jethro Beekman , Sean Christopherson , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH v6] x86/sgx: Free backing memory after faulting the enclave page Message-ID: References: <20220303223859.273187-1-jarkko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Mar 08, 2022 at 11:16:19AM -0800, Reinette Chatre wrote: > Hi, > > On 3/3/2022 2:38 PM, Jarkko Sakkinen wrote: > > There is a limited amount of SGX memory (EPC) on each system. When that > > memory is used up, SGX has its own swapping mechanism which is similar > > in concept but totally separate from the core mm/* code. Instead of > > swapping to disk, SGX swaps from EPC to normal RAM. That normal RAM > > comes from a shared memory pseudo-file and can itself be swapped by the > > core mm code. There is a hierarchy like this: > > > > EPC <-> shmem <-> disk > > > > After data is swapped back in from shmem to EPC, the shmem backing > > storage needs to be freed. Currently, the backing shmem is not freed. > > This effectively wastes the shmem while the enclave is running. The > > memory is recovered when the enclave is destroyed and the backing > > storage freed. > > > > Sort this out by freeing memory with shmem_truncate_range(), as soon as > > a page is faulted back to the EPC. In addition, free the memory for > > PCMD pages as soon as all PCMD's in a page have been marked as unused > > by zeroing its contents. > > > > Reported-by: Dave Hansen > > Cc: stable@vger.kernel.org > > Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") > > Signed-off-by: Jarkko Sakkinen > > I can reliably reproduce the issue this patch aims to solve by creating > a virtual machine that has a significant portion of its memory consumed > by EPC: > > qemu-system-x86_64 -smp 4 -m 4G\ > -enable-kvm \ > -cpu host,+sgx-provisionkey \ > -object memory-backend-ram,size=2G,host-nodes=0,policy=bind,id=node0 \ > -object memory-backend-epc,id=mem0,size=1536M,prealloc=on,host-nodes=0,policy=bind \ > -numa node,nodeid=0,cpus=0-1,memdev=node0 \ > -object memory-backend-ram,size=2G,host-nodes=1,policy=bind,id=node1 \ > -object memory-backend-epc,id=mem1,size=1536M,prealloc=on,host-nodes=1,policy=bind \ > -numa node,nodeid=1,cpus=2-3,memdev=node1 \ > -M sgx-epc.0.memdev=mem0,sgx-epc.0.node=0,sgx-epc.1.memdev=mem1,sgx-epc.1.node=1 \ > ... > > Before this patch, running the very stressful SGX2 over subscription test case > (unclobbered_vdso_oversubscribed_remove) in this environment always triggers > the oom-killer but no amount of tasks killed can save the system > with it always ending deadlocked on memory: > > [ 58.642719] Tasks state (memory values in pages): > [ 58.644324] [ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name > [ 58.647237] [ 195] 0 195 3153 197 45056 0 -1000 systemd-udevd > [ 58.650238] [ 281] 0 281 1836367 0 10817536 0 0 test_sgx > [ 58.653088] Out of memory and no killable processes... > [ 58.654832] Kernel panic - not syncing: System is deadlocked on memory > > After applying this patch I was able to run SGX2 selftest > unclobbered_vdso_oversubscribed_remove ten times successfully. > > Tested-by: Reinette Chatre Thank you. > Reinette BR, Jarkko