From patchwork Mon Nov 23 13:28:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 11925203 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,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 BA3EDC2D0E4 for ; Mon, 23 Nov 2020 13:28:55 +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 4E276206E3 for ; Mon, 23 Nov 2020 13:28:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="koWTdlgv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E276206E3 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com 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.34288.65221 (Exim 4.92) (envelope-from ) id 1khBte-0007kL-3K; Mon, 23 Nov 2020 13:28:46 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 34288.65221; Mon, 23 Nov 2020 13:28:46 +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" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBte-0007kE-0D; Mon, 23 Nov 2020 13:28:46 +0000 Received: by outflank-mailman (input) for mailman id 34288; Mon, 23 Nov 2020 13:28:45 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBtc-0007k0-Ty for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 13:28:44 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 1efc338a-1c06-4c6c-b64a-8e394327c95a; Mon, 23 Nov 2020 13:28:44 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4089EACC6; Mon, 23 Nov 2020 13:28:43 +0000 (UTC) Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBtc-0007k0-Ty for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 13:28:44 +0000 X-Inumbo-ID: 1efc338a-1c06-4c6c-b64a-8e394327c95a Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 1efc338a-1c06-4c6c-b64a-8e394327c95a; Mon, 23 Nov 2020 13:28:44 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1606138123; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u2CaRag6/oUqYllh9jVd06ZD4oOB0HabLrsdZBZjXfs=; b=koWTdlgvz4DaO2jfk3SOuhmqC1wZ9ssswhghaExLgcbamSKMFK7KHqaiIZuaBDIML+5ZpJ f/JWg62SDspsjzxd2s0574g2S9PSEuff+9DkVPmlvnw1Z5NO1fRkMAU4wc52WvJTg1iefG AuERTJ6ZiQmbcNZ6k8AAUuWsgNIfAxA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4089EACC6; Mon, 23 Nov 2020 13:28:43 +0000 (UTC) Subject: [PATCH v3 3/5] evtchn: convert vIRQ lock to an r/w one From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Wei Liu , Stefano Stabellini References: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> Message-ID: Date: Mon, 23 Nov 2020 14:28:42 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> Content-Language: en-US There's no need to serialize all sending of vIRQ-s; all that's needed is serialization against the closing of the respective event channels (so far by means of a barrier). To facilitate the conversion, switch to an ordinary write locked region in evtchn_close(). Signed-off-by: Jan Beulich Reviewed-by: Julien Grall --- v3: Re-base over added new earlier patch. v2: Don't introduce/use rw_barrier() here. Add comment to evtchn_bind_virq(). Re-base. --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -160,7 +160,7 @@ struct vcpu *vcpu_create(struct domain * v->vcpu_id = vcpu_id; v->dirty_cpu = VCPU_CPU_CLEAN; - spin_lock_init(&v->virq_lock); + rwlock_init(&v->virq_lock); tasklet_init(&v->continue_hypercall_tasklet, NULL, NULL); --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -475,6 +475,13 @@ int evtchn_bind_virq(evtchn_bind_virq_t evtchn_write_unlock(chn); bind->port = port; + /* + * If by any, the update of virq_to_evtchn[] would need guarding by + * virq_lock, but since this is the last action here, there's no strict + * need to acquire the lock. Hence holding event_lock isn't helpful + * anymore at this point, but utilize that its unlocking acts as the + * otherwise necessary smp_wmb() here. + */ write_atomic(&v->virq_to_evtchn[virq], port); out: @@ -661,10 +668,12 @@ int evtchn_close(struct domain *d1, int case ECS_VIRQ: for_each_vcpu ( d1, v ) { - if ( read_atomic(&v->virq_to_evtchn[chn1->u.virq]) != port1 ) - continue; - write_atomic(&v->virq_to_evtchn[chn1->u.virq], 0); - spin_barrier(&v->virq_lock); + unsigned long flags; + + write_lock_irqsave(&v->virq_lock, flags); + if ( read_atomic(&v->virq_to_evtchn[chn1->u.virq]) == port1 ) + write_atomic(&v->virq_to_evtchn[chn1->u.virq], 0); + write_unlock_irqrestore(&v->virq_lock, flags); } break; @@ -813,7 +822,7 @@ void send_guest_vcpu_virq(struct vcpu *v ASSERT(!virq_is_global(virq)); - spin_lock_irqsave(&v->virq_lock, flags); + read_lock_irqsave(&v->virq_lock, flags); port = read_atomic(&v->virq_to_evtchn[virq]); if ( unlikely(port == 0) ) @@ -823,7 +832,7 @@ void send_guest_vcpu_virq(struct vcpu *v evtchn_port_set_pending(d, v->vcpu_id, evtchn_from_port(d, port)); out: - spin_unlock_irqrestore(&v->virq_lock, flags); + read_unlock_irqrestore(&v->virq_lock, flags); } void send_guest_global_virq(struct domain *d, uint32_t virq) @@ -842,7 +851,7 @@ void send_guest_global_virq(struct domai if ( unlikely(v == NULL) ) return; - spin_lock_irqsave(&v->virq_lock, flags); + read_lock_irqsave(&v->virq_lock, flags); port = read_atomic(&v->virq_to_evtchn[virq]); if ( unlikely(port == 0) ) @@ -852,7 +861,7 @@ void send_guest_global_virq(struct domai evtchn_port_set_pending(d, chn->notify_vcpu_id, chn); out: - spin_unlock_irqrestore(&v->virq_lock, flags); + read_unlock_irqrestore(&v->virq_lock, flags); } void send_guest_pirq(struct domain *d, const struct pirq *pirq) --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -238,7 +238,7 @@ struct vcpu /* IRQ-safe virq_lock protects against delivering VIRQ to stale evtchn. */ evtchn_port_t virq_to_evtchn[NR_VIRQS]; - spinlock_t virq_lock; + rwlock_t virq_lock; /* Tasklet for continue_hypercall_on_cpu(). */ struct tasklet continue_hypercall_tasklet;