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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 CC717C2D0A3 for ; Fri, 6 Nov 2020 16:32:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C70321556 for ; Fri, 6 Nov 2020 16:32:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Gd9fdaex" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726765AbgKFQcT (ORCPT ); Fri, 6 Nov 2020 11:32:19 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:42871 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726034AbgKFQcT (ORCPT ); Fri, 6 Nov 2020 11:32:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604680337; h=from:from:reply-to:subject:subject: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=+T0wh6v8l6lQUrvw4s9+AbRJQ2Z4GCUXzV2HD9+48LQ=; b=Gd9fdaexEpytto1wLRYrfQavVEFPbNkzrkwnVX20MLvESGqvcwKEFnsgLEhXavWZZuTglM 8lgm7fm7oN/zWOzImmOhfS2JcCU0XAOSmT7IvnTEx25T+NpO5kcLT+BLfJgy3AxlgD4FfY 63jo/DHArXq0vyHZF3A3xK/vV+N2kWg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-334-hcRXZq1dPjaMDveOEJbP9Q-1; Fri, 06 Nov 2020 11:32:15 -0500 X-MC-Unique: hcRXZq1dPjaMDveOEJbP9Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 32D5A802B45; Fri, 6 Nov 2020 16:32:14 +0000 (UTC) Received: from w520.home (ovpn-112-213.phx2.redhat.com [10.3.112.213]) by smtp.corp.redhat.com (Postfix) with ESMTP id 602CE2619E; Fri, 6 Nov 2020 16:32:01 +0000 (UTC) Date: Fri, 6 Nov 2020 09:32:00 -0700 From: Alex Williamson To: Paolo Bonzini Cc: David Woodhouse , Peter Zijlstra , linux-kernel@vger.kernel.org, Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , kvm@vger.kernel.org Subject: Re: [PATCH v2 1/2] sched/wait: Add add_wait_queue_priority() Message-ID: <20201106093200.6d8975ae@w520.home> In-Reply-To: References: <20201026175325.585623-1-dwmw2@infradead.org> <20201027143944.648769-1-dwmw2@infradead.org> <20201027143944.648769-2-dwmw2@infradead.org> <20201028143509.GA2628@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Nov 2020 11:17:21 +0100 Paolo Bonzini wrote: > On 04/11/20 10:35, David Woodhouse wrote: > > On Wed, 2020-10-28 at 15:35 +0100, Peter Zijlstra wrote: > >> On Tue, Oct 27, 2020 at 02:39:43PM +0000, David Woodhouse wrote: > >>> From: David Woodhouse > >>> > >>> This allows an exclusive wait_queue_entry to be added at the head of the > >>> queue, instead of the tail as normal. Thus, it gets to consume events > >>> first without allowing non-exclusive waiters to be woken at all. > >>> > >>> The (first) intended use is for KVM IRQFD, which currently has > >>> inconsistent behaviour depending on whether posted interrupts are > >>> available or not. If they are, KVM will bypass the eventfd completely > >>> and deliver interrupts directly to the appropriate vCPU. If not, events > >>> are delivered through the eventfd and userspace will receive them when > >>> polling on the eventfd. > >>> > >>> By using add_wait_queue_priority(), KVM will be able to consistently > >>> consume events within the kernel without accidentally exposing them > >>> to userspace when they're supposed to be bypassed. This, in turn, means > >>> that userspace doesn't have to jump through hoops to avoid listening > >>> on the erroneously noisy eventfd and injecting duplicate interrupts. > >>> > >>> Signed-off-by: David Woodhouse > >> > >> Acked-by: Peter Zijlstra (Intel) > > > > Thanks. Paolo, the conclusion was that you were going to take this set > > through the KVM tree, wasn't it? > > > > Queued, except for patch 2/3 in the eventfd series which Alex hasn't > reviewed/acked yet. There was no vfio patch here, nor mention why it got dropped in v2 afaict. Thanks, Alex