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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 96BBAC07E99 for ; Fri, 9 Jul 2021 13:21:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 806F2608FE for ; Fri, 9 Jul 2021 13:21:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232422AbhGINYi (ORCPT ); Fri, 9 Jul 2021 09:24:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:56216 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232725AbhGINYb (ORCPT ); Fri, 9 Jul 2021 09:24:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0F54A613C3; Fri, 9 Jul 2021 13:21:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1625836907; bh=3oliXGR9Qmog+iZxulDaz4OOaDbFdfAQ3V6ap1M167c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w0cZD17O8IP+SMmj13GaG2eXLlUdMfAgkU/oZy6ZcNv420qfYAbu+i8MM+T4AlXht 8qtfdeSeCaCrtvz8hR+MeEnj5Qdi+AzPglJdcfZ/4nx36afaZ0q+XAT1DoBAoMkY4S 2OGBTP04HhHhhoqqJHYHohdCpA3iG0+ARol4kJGg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Rientjes , Paolo Bonzini , "Nobuhiro Iwamatsu (CIP)" Subject: [PATCH 4.19 25/34] KVM: SVM: Periodically schedule when unregistering regions on destroy Date: Fri, 9 Jul 2021 15:20:41 +0200 Message-Id: <20210709131658.126237524@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210709131644.969303901@linuxfoundation.org> References: <20210709131644.969303901@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: David Rientjes commit 7be74942f184fdfba34ddd19a0d995deb34d4a03 upstream. There may be many encrypted regions that need to be unregistered when a SEV VM is destroyed. This can lead to soft lockups. For example, on a host running 4.15: watchdog: BUG: soft lockup - CPU#206 stuck for 11s! [t_virtual_machi:194348] CPU: 206 PID: 194348 Comm: t_virtual_machi RIP: 0010:free_unref_page_list+0x105/0x170 ... Call Trace: [<0>] release_pages+0x159/0x3d0 [<0>] sev_unpin_memory+0x2c/0x50 [kvm_amd] [<0>] __unregister_enc_region_locked+0x2f/0x70 [kvm_amd] [<0>] svm_vm_destroy+0xa9/0x200 [kvm_amd] [<0>] kvm_arch_destroy_vm+0x47/0x200 [<0>] kvm_put_kvm+0x1a8/0x2f0 [<0>] kvm_vm_release+0x25/0x30 [<0>] do_exit+0x335/0xc10 [<0>] do_group_exit+0x3f/0xa0 [<0>] get_signal+0x1bc/0x670 [<0>] do_signal+0x31/0x130 Although the CLFLUSH is no longer issued on every encrypted region to be unregistered, there are no other changes that can prevent soft lockups for very large SEV VMs in the latest kernel. Periodically schedule if necessary. This still holds kvm->lock across the resched, but since this only happens when the VM is destroyed this is assumed to be acceptable. Signed-off-by: David Rientjes Message-Id: Signed-off-by: Paolo Bonzini [iwamatsu: adjust filename.] Reference: CVE-2020-36311 Signed-off-by: Nobuhiro Iwamatsu (CIP) Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1954,6 +1954,7 @@ static void sev_vm_destroy(struct kvm *k list_for_each_safe(pos, q, head) { __unregister_enc_region_locked(kvm, list_entry(pos, struct enc_region, list)); + cond_resched(); } }