From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48894) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bQXQW-0003G6-9Q for qemu-devel@nongnu.org; Fri, 22 Jul 2016 06:11:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bQXQQ-0008Q8-7M for qemu-devel@nongnu.org; Fri, 22 Jul 2016 06:11:27 -0400 Received: from 2.mo178.mail-out.ovh.net ([46.105.39.61]:48129) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bQXQQ-0008Pe-1A for qemu-devel@nongnu.org; Fri, 22 Jul 2016 06:11:22 -0400 Received: from player169.ha.ovh.net (b9.ovh.net [213.186.33.59]) by mo178.mail-out.ovh.net (Postfix) with ESMTP id B1E5D100498C for ; Fri, 22 Jul 2016 12:11:20 +0200 (CEST) Date: Fri, 22 Jul 2016 12:11:11 +0200 From: Greg Kurz Message-ID: <20160722121111.4626226f@bahia.lan> In-Reply-To: <20160722100435.1cf57293.cornelia.huck@de.ibm.com> References: <146913602256.26732.547184422534259409.stgit@bahia.lan> <20160722100435.1cf57293.cornelia.huck@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4] virtio-pci: error out when both legacy and modern modes are disabled List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: "Michael S. Tsirkin" , Eric Blake , qemu-devel@nongnu.org, Marcel Apfelbaum On Fri, 22 Jul 2016 10:04:35 +0200 Cornelia Huck wrote: > On Thu, 21 Jul 2016 23:21:16 +0200 > Greg Kurz wrote: > > > From: Greg Kurz > > > > Without presuming if we got there because of a user mistake or some > > more subtle bug in the tooling, it really does not make sense to > > implement a non-functional device. > > > > Signed-off-by: Greg Kurz > > Reviewed-by: Marcel Apfelbaum > > Signed-off-by: Greg Kurz > > --- > > v4: - rephrased error message and provide a hint to the user > > - split string literals to stay below 80 characters > > - added Marcel's R-b tag > > --- > > hw/virtio/virtio-pci.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > > index 755f9218b77d..72c4b392ffda 100644 > > --- a/hw/virtio/virtio-pci.c > > +++ b/hw/virtio/virtio-pci.c > > @@ -1842,6 +1842,14 @@ static void virtio_pci_dc_realize(DeviceState *qdev, Error **errp) > > VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev); > > PCIDevice *pci_dev = &proxy->pci_dev; > > > > + if (!(virtio_pci_modern(proxy) || virtio_pci_legacy(proxy))) { > > I'm not sure that I didn't mess up the sequence of the realize > callbacks, but could disable_legacy still be AUTO here? In that case, > we'd fail for disable-modern=on and disable-legacy unset (i.e., AUTO), > which would be ok for pcie but not for !pcie. > Marcel made the same comment in: https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg05225.html If the user explicitly disables modern, she shouldn't rely on QEMU implicitly enabling legacy, hence the suggestion in error_append_hint(). > > + error_setg(errp, "device cannot work when both modern and legacy modes" > > + " are disabled"); > > + error_append_hint(errp, "Set either disable-modern or disable-legacy" > > + " to off\n"); > > + return; > > + } > > + > > if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) && > > virtio_pci_modern(proxy)) { > > pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS; > > >