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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 DDE2CC64E7B for ; Wed, 2 Dec 2020 21:14:46 +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 63CEA21D91 for ; Wed, 2 Dec 2020 21:14:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 63CEA21D91 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.43016.77398 (Exim 4.92) (envelope-from ) id 1kkZSP-0001Qt-It; Wed, 02 Dec 2020 21:14:37 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 43016.77398; Wed, 02 Dec 2020 21:14:37 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkZSP-0001Qm-FD; Wed, 02 Dec 2020 21:14:37 +0000 Received: by outflank-mailman (input) for mailman id 43016; Wed, 02 Dec 2020 21:14:36 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkZSO-0001Qh-Om for xen-devel@lists.xenproject.org; Wed, 02 Dec 2020 21:14:36 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkZSM-0003wn-Jr; Wed, 02 Dec 2020 21:14:34 +0000 Received: from [54.239.6.186] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1kkZSM-0003Ud-DL; Wed, 02 Dec 2020 21:14:34 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=PMNxof0t/q+zpIFpcEyHRgoWAfoohyTYPUe/y/T+DLU=; b=iljXsA1wn7crLPV6J1kB4AgqpT mmmtzAxW/BHVlHYBXM9Ds+cVgA+EFIwNXXRXuSOSjOzVjKnwPiobpnFPO588kRJUWBrEt1bQedYlm axy0EqBOfY3gZBqb6cZKxCIEadYC3YK3IJ2kFBvmVUcgMA0/FGK8w5VPZbin99kPJ+iM=; Subject: Re: [PATCH v3 2/5] evtchn: avoid access tearing for ->virq_to_evtchn[] accesses To: Jan Beulich , "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Ian Jackson , Wei Liu , Stefano Stabellini References: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> From: Julien Grall Message-ID: Date: Wed, 2 Dec 2020 21:14:32 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Jan, On 23/11/2020 13:28, Jan Beulich wrote: > Use {read,write}_atomic() to exclude any eventualities, in particular > observing that accesses aren't all happening under a consistent lock. > > Requested-by: Julien Grall > Signed-off-by: Jan Beulich Reviewed-by: Julien Grall Cheers, > --- > v3: New. > > --- a/xen/common/event_channel.c > +++ b/xen/common/event_channel.c > @@ -446,7 +446,7 @@ int evtchn_bind_virq(evtchn_bind_virq_t > > spin_lock(&d->event_lock); > > - if ( v->virq_to_evtchn[virq] != 0 ) > + if ( read_atomic(&v->virq_to_evtchn[virq]) ) > ERROR_EXIT(-EEXIST); > > if ( port != 0 ) > @@ -474,7 +474,8 @@ int evtchn_bind_virq(evtchn_bind_virq_t > > evtchn_write_unlock(chn); > > - v->virq_to_evtchn[virq] = bind->port = port; > + bind->port = port; > + write_atomic(&v->virq_to_evtchn[virq], port); > > out: > spin_unlock(&d->event_lock); > @@ -660,9 +661,9 @@ int evtchn_close(struct domain *d1, int > case ECS_VIRQ: > for_each_vcpu ( d1, v ) > { > - if ( v->virq_to_evtchn[chn1->u.virq] != port1 ) > + if ( read_atomic(&v->virq_to_evtchn[chn1->u.virq]) != port1 ) > continue; > - v->virq_to_evtchn[chn1->u.virq] = 0; > + write_atomic(&v->virq_to_evtchn[chn1->u.virq], 0); > spin_barrier(&v->virq_lock); > } > break; > @@ -801,7 +802,7 @@ bool evtchn_virq_enabled(const struct vc > if ( virq_is_global(virq) && v->vcpu_id ) > v = domain_vcpu(v->domain, 0); > > - return v->virq_to_evtchn[virq]; > + return read_atomic(&v->virq_to_evtchn[virq]); > } > > void send_guest_vcpu_virq(struct vcpu *v, uint32_t virq) > @@ -814,7 +815,7 @@ void send_guest_vcpu_virq(struct vcpu *v > > spin_lock_irqsave(&v->virq_lock, flags); > > - port = v->virq_to_evtchn[virq]; > + port = read_atomic(&v->virq_to_evtchn[virq]); > if ( unlikely(port == 0) ) > goto out; > > @@ -843,7 +844,7 @@ void send_guest_global_virq(struct domai > > spin_lock_irqsave(&v->virq_lock, flags); > > - port = v->virq_to_evtchn[virq]; > + port = read_atomic(&v->virq_to_evtchn[virq]); > if ( unlikely(port == 0) ) > goto out; > > -- Julien Grall