From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PULL 4/5] vfio-pci: Add debug config options to disable MSI/X KVM support Date: Mon, 09 Dec 2013 10:48:59 +0100 Message-ID: <52A5920B.2040601@redhat.com> References: <20131206204715.16731.12627.stgit@bling.home> <20131206204842.16731.29998.stgit@bling.home> <52A24A6A.6000809@redhat.com> <1386369360.25738.523.camel@ul30vt.home> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: aliguori@amazon.com, qemu-devel@nongnu.org, kvm@vger.kernel.org To: Alex Williamson Return-path: Received: from mx1.redhat.com ([209.132.183.28]:56598 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932203Ab3LIJtF (ORCPT ); Mon, 9 Dec 2013 04:49:05 -0500 In-Reply-To: <1386369360.25738.523.camel@ul30vt.home> Sender: kvm-owner@vger.kernel.org List-ID: Il 06/12/2013 23:36, Alex Williamson ha scritto: >>> > > #define VFIO_ALLOW_MMAP 1 >>> > > #define VFIO_ALLOW_KVM_INTX 1 >>> > > +#define VFIO_ALLOW_KVM_MSI 1 >>> > > +#define VFIO_ALLOW_KVM_MSIX 1 >> > >> > Why not make these device properties instead? > Honestly, I don't think they're that useful to the average or even to > the advanced user. Each of these disables an acceleration/bypass path > and gives more logging output when debug is enabled. Otherwise we don't > get debugging to see when mmap'd BARs are accessed and we can't tell > when interrupts happen relative to other accesses. For instance it was > pretty obvious to find the Nvidia MSI ACK when seeing a config space > write immediately following an MSI injection. Without debugging > enabled, these just slow things down and I don't know of any cases where > a device behaves better with these features disabled. Yeah, behaving better is unlikely. I was thinking of them as a debugging features. As to debug messages, have you considered replacing them with tracepoints? Paolo