From patchwork Mon Nov 9 06:41:27 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: 11890511 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 07F93921 for ; Mon, 9 Nov 2020 06:43:05 +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 C33C0206C0 for ; Mon, 9 Nov 2020 06:43:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="vHcHmS9u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C33C0206C0 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.21985.48345 (Exim 4.92) (envelope-from ) id 1kc0ry-00019H-Rj; Mon, 09 Nov 2020 06:41:38 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 21985.48345; Mon, 09 Nov 2020 06:41:38 +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 1kc0ry-000194-OA; Mon, 09 Nov 2020 06:41:38 +0000 Received: by outflank-mailman (input) for mailman id 21985; Mon, 09 Nov 2020 06:41:37 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kc0rx-00015b-HR for xen-devel@lists.xenproject.org; Mon, 09 Nov 2020 06:41:37 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f; Mon, 09 Nov 2020 06:41:31 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AEF18ABCC; Mon, 9 Nov 2020 06:41:30 +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 1kc0rx-00015b-HR for xen-devel@lists.xenproject.org; Mon, 09 Nov 2020 06:41:37 +0000 X-Inumbo-ID: 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f; Mon, 09 Nov 2020 06:41:31 +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=1604904090; 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=DpSBXBI2OHigxodLIbPPZp3jSMwO4fg1IhybSfwcpsI=; b=vHcHmS9uJ5nMjtGus5KwQC5iOMcryUTUzOTi7GicoBnf5dhxpv8DMsx7jhwvCZfXmQj77i h2Vfpcvhmye3DCCyUi3ffHjp0+fEPzhcAwKwcBGuhTGN8yC54o3+L9A0SMR7u1xhVL2kS7 LaxgeFlgZSfsGt1TR3pk2av2fSUQdDk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AEF18ABCC; Mon, 9 Nov 2020 06:41:30 +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 , Julien Grall Subject: [PATCH v5 1/2] xen/events: access last_priority and last_vcpu_id together Date: Mon, 9 Nov 2020 07:41:27 +0100 Message-Id: <20201109064128.3908-2-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201109064128.3908-1-jgross@suse.com> References: <20201109064128.3908-1-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 Reviewed-by: Julien Grall --- 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 c6e58d2a1a..79090c04ca 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 { + uint32_t raw; + struct { + uint8_t last_priority; + uint16_t 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