From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756077AbZD2ITu (ORCPT ); Wed, 29 Apr 2009 04:19:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752042AbZD2ITd (ORCPT ); Wed, 29 Apr 2009 04:19:33 -0400 Received: from mx2.redhat.com ([66.187.237.31]:60780 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751288AbZD2ITb (ORCPT ); Wed, 29 Apr 2009 04:19:31 -0400 Message-ID: <49F80D67.8030008@redhat.com> Date: Wed, 29 Apr 2009 11:18:47 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Andrew Morton CC: Gregory Haskins , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, davidel@xmailserver.org Subject: Re: [KVM PATCH v3 0/2] irqfd References: <20090427182540.6646.96740.stgit@dev.haskins.net> <20090428231002.919419dd.akpm@linux-foundation.org> In-Reply-To: <20090428231002.919419dd.akpm@linux-foundation.org> Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Mon, 27 Apr 2009 14:33:24 -0400 Gregory Haskins wrote: > > >> (Applies to kvm.git 41b76d8d0487c26d6d4d3fe53c1ff59b3236f096) >> >> This series implements a mechanism called "irqfd". It lets you create >> an eventfd based file-desriptor to inject interrupts to a kvm guest. We >> associate one gsi per fd for fine-grained routing. >> > > It'd be nice if the KVM weenies amongst us were to be told why one > would want to inject interrupts into a KVM guest. Monosyllabic words > would be preferred ;) > Interrupts are injected (better word, raised) into a guest because real hardware has interrupts. This patchset does not add the ability to raise interrupts (that existed from day 1); it adds an eventfd interface to do so. An eventfd interface is useful, because it allows components to talk to kvm guests without being tied to kvm internals; they signal an eventfd; if the eventfd is terminated in kvm, it injects an interrupt. If the eventfd is terminated in userspace, it returns from epoll(). >> We do not have a user of this interface in this series, though note >> future version of virtual-bus (v4 and above) will be based on this. >> > > So I assume that this patchset will be merged if/when a user of it is > merged? > This interface is applicable to both the kernel and userspace; userspace users won't be merged. But I certainly want to see how the whole thing works. >> The first patch will require mainline buy-in, particularly from Davide >> (cc'd). The last patch is kvm specific. >> > > Three EXPORT_SYMBOL_GPL()s. Once the shouting has subsided I'd suggest > that this be merged via the KVM tree. > I think eventfd makes tons of sense as a generic 'wake me up' mechanism that can be used from both sides of the kernel/user line. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.