From patchwork Mon Nov 4 13:58:12 2019 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: 11225851 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 E239214E5 for ; Mon, 4 Nov 2019 14:00:14 +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 C7D5621D71 for ; Mon, 4 Nov 2019 14:00:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C7D5621D71 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 1iRcsQ-0006uD-QV; Mon, 04 Nov 2019 13:58:38 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iRcsQ-0006u7-5D for xen-devel@lists.xenproject.org; Mon, 04 Nov 2019 13:58:38 +0000 X-Inumbo-ID: 31e26734-ff0b-11e9-b678-bc764e2007e4 Received: from mx1.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 31e26734-ff0b-11e9-b678-bc764e2007e4; Mon, 04 Nov 2019 13:58:36 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 56D91B417; Mon, 4 Nov 2019 13:58:35 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Date: Mon, 4 Nov 2019 14:58:12 +0100 Message-Id: <20191104135812.2314-1-jgross@suse.com> X-Mailer: git-send-email 2.16.4 Subject: [Xen-devel] [PATCH] xen/events: remove event handling recursion detection 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 , Boris Ostrovsky , Stefano Stabellini MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" __xen_evtchn_do_upcall() contains guards against being called recursively. This mechanism was introduced in the early pvops times (kernel 2.6.26) when there were still Xen versions around not honoring disabled interrupts for sending events to pv guests. This was changed in Xen 3.0, which is much older than any Xen version supported by the kernel, so the recursion detection can be removed. Signed-off-by: Juergen Gross --- drivers/xen/events/events_base.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 6c8843968a52..33212c494afd 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -1213,31 +1213,21 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector) notify_remote_via_irq(irq); } -static DEFINE_PER_CPU(unsigned, xed_nesting_count); - static void __xen_evtchn_do_upcall(void) { struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu); - int cpu = get_cpu(); - unsigned count; + int cpu = smp_processor_id(); do { vcpu_info->evtchn_upcall_pending = 0; - if (__this_cpu_inc_return(xed_nesting_count) - 1) - goto out; - xen_evtchn_handle_events(cpu); BUG_ON(!irqs_disabled()); - count = __this_cpu_read(xed_nesting_count); - __this_cpu_write(xed_nesting_count, 0); - } while (count != 1 || vcpu_info->evtchn_upcall_pending); - -out: + rmb(); /* Hypervisor can set upcall pending. */ - put_cpu(); + } while (vcpu_info->evtchn_upcall_pending); } void xen_evtchn_do_upcall(struct pt_regs *regs)