From patchwork Mon Oct 12 09:10:57 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: 11831991 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 833A092C for ; Mon, 12 Oct 2020 09:12:31 +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 4811C206B5 for ; Mon, 12 Oct 2020 09:12:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="UQVVEfJ9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4811C206B5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none 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.5824.15131 (Exim 4.92) (envelope-from ) id 1kRtrI-0005Gi-4z; Mon, 12 Oct 2020 09:11:08 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 5824.15131; Mon, 12 Oct 2020 09:11:08 +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 1kRtrI-0005Gb-1Z; Mon, 12 Oct 2020 09:11:08 +0000 Received: by outflank-mailman (input) for mailman id 5824; Mon, 12 Oct 2020 09:11:06 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kRtrG-0005GU-6V for xen-devel@lists.xenproject.org; Mon, 12 Oct 2020 09:11:06 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id fa7f867d-7762-43b6-ae41-1608beac901c; Mon, 12 Oct 2020 09:11:02 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5F9BEB03D; Mon, 12 Oct 2020 09:11:01 +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 1kRtrG-0005GU-6V for xen-devel@lists.xenproject.org; Mon, 12 Oct 2020 09:11:06 +0000 X-Inumbo-ID: fa7f867d-7762-43b6-ae41-1608beac901c Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id fa7f867d-7762-43b6-ae41-1608beac901c; Mon, 12 Oct 2020 09:11:02 +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=1602493861; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SYSqKrZWGVU8nxonrOSCcTNQRNTPVy8fH0KXNbdNrqQ=; b=UQVVEfJ95n3dY3iu7GzrIgq7zCx6w88hoYhCakpqGLOl2YZ9H6Ss4ezICtUjHacArx1Yh0 SeptfKSuohJ0y89iYiYJ5qm93EOoYxJODDSX347hFr03NZJ6D2L02a1NNZqkZUCUlmRB+V 0/aZ1d/CpcQ+Xe0QVFXp1Km/xpEF28g= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5F9BEB03D; Mon, 12 Oct 2020 09:11:01 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu Subject: [PATCH 1/2] xen/events: access last_priority and last_vcpu_id together Date: Mon, 12 Oct 2020 11:10:57 +0200 Message-Id: <20201012091058.27023-2-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201012091058.27023-1-jgross@suse.com> References: <20201012091058.27023-1-jgross@suse.com> MIME-Version: 1.0 The queue for a fifo event is depending on the vcpu_id and the priority of the event. When sending an event it might happen the event needs to change queues and the old queue needs to be kept for keeping the links between queue elements intact. For this purpose the event channel contains last_priority and last_vcpu_id values elements for being able to identify the old queue. In order to avoid races always access last_priority and last_vcpu_id with a single atomic operation avoiding any inconsistencies. Signed-off-by: Juergen Gross --- xen/common/event_fifo.c | 25 +++++++++++++++++++------ xen/include/xen/sched.h | 3 +-- 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c index fc189152e1..fffbd409c8 100644 --- a/xen/common/event_fifo.c +++ b/xen/common/event_fifo.c @@ -42,6 +42,14 @@ struct evtchn_fifo_domain { unsigned int num_evtchns; }; +union evtchn_fifo_lastq { + u32 raw; + struct { + u8 last_priority; + u16 last_vcpu_id; + }; +}; + static inline event_word_t *evtchn_fifo_word_from_port(const struct domain *d, unsigned int port) { @@ -86,16 +94,18 @@ static struct evtchn_fifo_queue *lock_old_queue(const struct domain *d, struct vcpu *v; struct evtchn_fifo_queue *q, *old_q; unsigned int try; + union evtchn_fifo_lastq lastq; for ( try = 0; try < 3; try++ ) { - v = d->vcpu[evtchn->last_vcpu_id]; - old_q = &v->evtchn_fifo->queue[evtchn->last_priority]; + lastq.raw = read_atomic(&evtchn->fifo_lastq); + v = d->vcpu[lastq.last_vcpu_id]; + old_q = &v->evtchn_fifo->queue[lastq.last_priority]; spin_lock_irqsave(&old_q->lock, *flags); - v = d->vcpu[evtchn->last_vcpu_id]; - q = &v->evtchn_fifo->queue[evtchn->last_priority]; + v = d->vcpu[lastq.last_vcpu_id]; + q = &v->evtchn_fifo->queue[lastq.last_priority]; if ( old_q == q ) return old_q; @@ -246,8 +256,11 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct evtchn *evtchn) /* Moved to a different queue? */ if ( old_q != q ) { - evtchn->last_vcpu_id = v->vcpu_id; - evtchn->last_priority = q->priority; + union evtchn_fifo_lastq lastq; + + lastq.last_vcpu_id = v->vcpu_id; + lastq.last_priority = q->priority; + write_atomic(&evtchn->fifo_lastq, lastq.raw); spin_unlock_irqrestore(&old_q->lock, flags); spin_lock_irqsave(&q->lock, flags); diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index d8ed83f869..a298ff4df8 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -114,8 +114,7 @@ struct evtchn u16 virq; /* state == ECS_VIRQ */ } u; u8 priority; - u8 last_priority; - u16 last_vcpu_id; + u32 fifo_lastq; /* Data for fifo events identifying last queue. */ #ifdef CONFIG_XSM union { #ifdef XSM_NEED_GENERIC_EVTCHN_SSID