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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 E6E9BC48BC2 for ; Wed, 23 Jun 2021 13:32:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA75B6113B for ; Wed, 23 Jun 2021 13:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231348AbhFWNet (ORCPT ); Wed, 23 Jun 2021 09:34:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:43598 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231238AbhFWNej (ORCPT ); Wed, 23 Jun 2021 09:34:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5FD1561076; Wed, 23 Jun 2021 13:32:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624455141; bh=Tfy4Kcl1G/62IHsG83uwh+nanQpJpW+dZHtJIAsstRk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aaC5aBQGG9oOd0TrvI+dVAmmjAlInqOJnfdrBcfrhVFc8HQL7MvQqQpeWCWDkgkEj Zkg5806GK0IJU0VDsc2iY2Yd1F/aSQQfwB03j8ca2P7AevQR4nY++R+5eBy4ZjdmVZ 8GUVtWy1tTv5w5rAqmQ9RyNWQDXtmzyXMoc2GtQ0jmu0IUqlkvwni8ZWTJoqyZf4oZ cU1MEDNpUeWjsqoaExkMcNFI6ztE0sp1pfbAvVcbfbFOIXTl7yk3A+BqfXo2ZApsR0 yvcAOfB5UWQGhWlD5+cSZ3w4Qb+pZZSamsIYQWzxgDcvuJ2oXXLTOB2HUg6hK2X588 edtostLAVEdMw== Date: Wed, 23 Jun 2021 16:32:19 +0300 From: Jarkko Sakkinen To: Du Cheng Cc: Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, Dave Hansen , "H. Peter Anvin" , linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/sgx: Suppress WARN on inability to sanitize EPC if ksgxd is stopped Message-ID: <20210623133219.v6c62zwtj5qowib3@kernel.org> References: <20210616004458.2192889-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Wed, Jun 16, 2021 at 02:03:09PM +0800, Du Cheng wrote: > Le Tue, Jun 15, 2021 at 05:44:58PM -0700, Sean Christopherson a écrit : > > Don't WARN on having unsanitized EPC pages if ksgxd is stopped early, > > e.g. if sgx_init() realizes there will be no downstream consumers of EPC. > > If ksgxd is stopped early, EPC pages may be left on the dirty list, but > > that's ok because ksgxd is only stopped if SGX initialization failed or > > if the kernel is going down. In either case, the EPC won't be used. > > > > This bug was exposed by the addition of KVM support, but has existed and > > was hittable since the original sanitization code was added. Prior to > > adding KVM support, if Launch Control was not fully enabled, e.g. when > > running on older hardware, sgx_init() bailed immediately before spawning > > ksgxd because X86_FEATURE_SGX was cleared if X86_FEATURE_SGX_LC was > > unsupported. > > > > With KVM support, sgx_drv_init() handles the X86_FEATURE_SGX_LC check > > manually, so now there's any easy-to-hit case where sgx_init() will spawn > > ksgxd and _then_ fail to initialize, which results in sgx_init() stopping > > ksgxd before it finishes sanitizing the EPC. > > > > Prior to KVM support, the bug was much harder to hit because it basically > > required char device registration to fail. > > > > Reported-by: Du Cheng > > Fixes: e7e0545299d8 ("x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections") > > Signed-off-by: Sean Christopherson > > --- > > > > Lightly tested due to lack of hardware. I hacked the flow to verify that > > stopping early will leave work pending, and that rechecking should_stop() > > suppress the resulting WARN. > > > > arch/x86/kernel/cpu/sgx/main.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > > index ad904747419e..fbad2b9625a5 100644 > > --- a/arch/x86/kernel/cpu/sgx/main.c > > +++ b/arch/x86/kernel/cpu/sgx/main.c > > @@ -425,7 +425,7 @@ static int ksgxd(void *p) > > __sgx_sanitize_pages(&sgx_dirty_page_list); > > > > /* sanity check: */ > > - WARN_ON(!list_empty(&sgx_dirty_page_list)); > > + WARN_ON(!list_empty(&sgx_dirty_page_list) && !kthread_should_stop()); > > > > while (!kthread_should_stop()) { > > if (try_to_freeze()) > > -- > > 2.32.0.272.g935e593368-goog > > > > I applied this patch on 5.13-rc6, and it no longer causes to trigger WARN_ON() > on my NUC: > > ``` > > [ 0.669411] PCI-DMA: Using software bounce buffering for IO (SWIOTLB) > [ 0.669412] software IO TLB: mapped [mem 0x0000000017cb9000-0x000000001bcb9000] (64MB) > [ 0.672788] platform rtc_cmos: registered platform RTC device (no PNP device found) > [ 0.672805] sgx: EPC section 0x30200000-0x35f7ffff > [ 0.674239] Initialise system trusted keyrings > [ 0.674254] Key type blacklist registered > > ``` > > Regards, > Du Cheng Can you thus give a tested-by for this? /Jarkko