From patchwork Fri Feb 28 07:19:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?SsO8cmdlbiBHcm/Dnw==?= X-Patchwork-Id: 11411633 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0322013A4 for ; Fri, 28 Feb 2020 07:20:41 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DC74F246A0 for ; Fri, 28 Feb 2020 07:20:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DC74F246A0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j7Zvk-0004Wz-2x; Fri, 28 Feb 2020 07:19:28 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j7Zvi-0004Wu-Sf for xen-devel@lists.xenproject.org; Fri, 28 Feb 2020 07:19:26 +0000 X-Inumbo-ID: a60b0900-59fa-11ea-989e-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id a60b0900-59fa-11ea-989e-12813bfff9fa; Fri, 28 Feb 2020 07:19:25 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 88361ADB5; Fri, 28 Feb 2020 07:19:24 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Fri, 28 Feb 2020 08:19:22 +0100 Message-Id: <20200228071922.3983-1-jgross@suse.com> X-Mailer: git-send-email 2.16.4 Subject: [Xen-devel] [PATCH v2] xen: make sure stop_machine_run() is always called in a tasklet X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Julien Grall , Wei Liu , Konrad Rzeszutek Wilk , Andrew Cooper , Ian Jackson , George Dunlap , Jan Beulich , =?utf-8?q?Roger_Pau_Monn=C3=A9?= MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" With core scheduling active it is mandatory for stop_machine_run() to be called in idle context only (so either during boot or in a tasklet), as otherwise a scheduling deadlock would occur: stop_machine_run() does a cpu rendezvous by activating a tasklet on all other cpus. In case stop_machine_run() was not called in an idle vcpu it would block scheduling the idle vcpu on its siblings with core scheduling being active, resulting in a hang. Put a BUG_ON() into stop_machine_run() to test for being called in an idle vcpu only and adapt the missing call site (ucode loading) to use a tasklet for calling stop_machine_run(). Signed-off-by: Juergen Gross --- V2: - rephrase commit message (Julien Grall) --- xen/arch/x86/microcode.c | 54 +++++++++++++++++++++++++++++------------------ xen/common/stop_machine.c | 1 + 2 files changed, 35 insertions(+), 20 deletions(-) diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c index 35c1d36cdc..4cf4e66b18 100644 --- a/xen/arch/x86/microcode.c +++ b/xen/arch/x86/microcode.c @@ -562,30 +562,18 @@ static int do_microcode_update(void *patch) return ret; } -int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) buf, unsigned long len) +struct ucode_buf { + unsigned int len; + char buffer[]; +}; + +static long microcode_update_helper(void *data) { int ret; - void *buffer; + struct ucode_buf *buffer = data; unsigned int cpu, updated; struct microcode_patch *patch; - if ( len != (uint32_t)len ) - return -E2BIG; - - if ( microcode_ops == NULL ) - return -EINVAL; - - buffer = xmalloc_bytes(len); - if ( !buffer ) - return -ENOMEM; - - ret = copy_from_guest(buffer, buf, len); - if ( ret ) - { - xfree(buffer); - return -EFAULT; - } - /* cpu_online_map must not change during update */ if ( !get_cpu_maps() ) { @@ -607,7 +595,7 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) buf, unsigned long len) return -EPERM; } - patch = parse_blob(buffer, len); + patch = parse_blob(buffer->buffer, buffer->len); xfree(buffer); if ( IS_ERR(patch) ) { @@ -700,6 +688,32 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) buf, unsigned long len) return ret; } +int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) buf, unsigned long len) +{ + int ret; + struct ucode_buf *buffer; + + if ( len != (uint32_t)len ) + return -E2BIG; + + if ( microcode_ops == NULL ) + return -EINVAL; + + buffer = xmalloc_flex_struct(struct ucode_buf, buffer, len); + if ( !buffer ) + return -ENOMEM; + + ret = copy_from_guest(buffer->buffer, buf, len); + if ( ret ) + { + xfree(buffer); + return -EFAULT; + } + buffer->len = len; + + return continue_hypercall_on_cpu(0, microcode_update_helper, buffer); +} + static int __init microcode_init(void) { /* diff --git a/xen/common/stop_machine.c b/xen/common/stop_machine.c index 33d9602217..fe7f7d4447 100644 --- a/xen/common/stop_machine.c +++ b/xen/common/stop_machine.c @@ -74,6 +74,7 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) int ret; BUG_ON(!local_irq_is_enabled()); + BUG_ON(!is_idle_vcpu(current)); /* cpu_online_map must not change. */ if ( !get_cpu_maps() )