From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752751Ab0IPJtX (ORCPT ); Thu, 16 Sep 2010 05:49:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51233 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751498Ab0IPJtW (ORCPT ); Thu, 16 Sep 2010 05:49:22 -0400 Date: Thu, 16 Sep 2010 11:43:24 +0200 From: "Michael S. Tsirkin" To: Gleb Natapov Cc: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context Message-ID: <20100916094324.GE20864@redhat.com> References: <20100915185417.GA3924@redhat.com> <20100916090256.GU3008@redhat.com> <20100916091054.GA20864@redhat.com> <20100916092553.GV3008@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100916092553.GV3008@redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 16, 2010 at 11:25:53AM +0200, Gleb Natapov wrote: > On Thu, Sep 16, 2010 at 11:10:55AM +0200, Michael S. Tsirkin wrote: > > On Thu, Sep 16, 2010 at 11:02:56AM +0200, Gleb Natapov wrote: > > > On Wed, Sep 15, 2010 at 08:54:17PM +0200, Michael S. Tsirkin wrote: > > > > To avoid bouncing irqfd injection out to workqueue context, > > > > we must support injecting irqs from local interrupt > > > > context. Doing this seems to only require disabling > > > > irqs locally. > > > > > > > > RFC, completely untested, x86 only. > > > > > > > > Thoughts? > > > > > > > We do not want to disable irqs for a long time and some of code paths > > > under lock involve looping over all cpus. For MSI injection path is > > > lockless and this is the only case that matters, > > > > MSI only appeared in rhel6, older guests still use level interrupts. > So they are already slow for other reasons. They are slower than MSI, but I do not want irqfd to be slower than ioctls. > > Which paths require looping over all cpus? Do PCI interrupts > > need this? > > > All interrupts need it. IOAPIC has a loop to find dst cpu for interrupt. > Pic has a loop to find cpu in virtual wire mode. > > -- > Gleb.