From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:42167) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TklMh-0000BT-DB for qemu-devel@nongnu.org; Mon, 17 Dec 2012 19:49:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TklMf-0004an-IY for qemu-devel@nongnu.org; Mon, 17 Dec 2012 19:48:59 -0500 Received: from cantor2.suse.de ([195.135.220.15]:52606 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TklMf-0004aW-9o for qemu-devel@nongnu.org; Mon, 17 Dec 2012 19:48:57 -0500 Message-ID: <50CFBD6C.9010709@suse.de> Date: Tue, 18 Dec 2012 01:48:44 +0100 From: =?ISO-8859-1?Q?Andreas_F=E4rber?= MIME-Version: 1.0 References: <20121217154521.GA28674@redhat.com> <50CF5CA2.7060800@suse.de> <50CF629A.4090005@redhat.com> <50CF6384.9040809@suse.de> <20121217204811.GB30842@redhat.com> <50CF8AE7.1090803@suse.de> <20121217211831.GA11153@redhat.com> <50CF97EB.9070200@suse.de> <20121217225852.GA12661@redhat.com> <50CFB51E.5030108@suse.de> <20121218003016.GA15241@redhat.com> In-Reply-To: <20121218003016.GA15241@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] virtio: make bindings typesafe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Anthony Liguori , Jan Kiszka , qemu-devel@nongnu.org, Alexander Graf , Christian Borntraeger , Paolo Bonzini , fred.konrad@greensocs.com Am 18.12.2012 01:30, schrieb Michael S. Tsirkin: > On Tue, Dec 18, 2012 at 01:13:18AM +0100, Andreas F=E4rber wrote: >> Am 17.12.2012 23:58, schrieb Michael S. Tsirkin: >>> On Mon, Dec 17, 2012 at 11:08:43PM +0100, Andreas F=E4rber wrote: >>>> Am 17.12.2012 22:18, schrieb Michael S. Tsirkin: >>>>> On Mon, Dec 17, 2012 at 10:13:11PM +0100, Andreas F=E4rber wrote: >>>>>> Am 17.12.2012 21:48, schrieb Michael S. Tsirkin: >>>>>>> On Mon, Dec 17, 2012 at 07:25:08PM +0100, Andreas F=E4rber wrote: >>>>>>>> Am 17.12.2012 19:21, schrieb Paolo Bonzini: >>>>>>>>> Il 17/12/2012 18:55, Andreas F=E4rber ha scritto: >>>>>>>>>> Am 17.12.2012 16:45, schrieb Michael S. Tsirkin: >>>>>>>>>>> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c >>>>>>>>>>> index 3ea4140..63ae888 100644 >>>>>>>>>>> --- a/hw/virtio-pci.c >>>>>>>>>>> +++ b/hw/virtio-pci.c >>>>>>>>>>> @@ -98,34 +98,34 @@ bool virtio_is_big_endian(void); >>>>>>>>>>> =20 >>>>>>>>>>> /* virtio device */ >>>>>>>>>>> =20 >>>>>>>>>>> -static void virtio_pci_notify(void *opaque, uint16_t vector) >>>>>>>>>>> +static void virtio_pci_notify(DeviceState *d, uint16_t vecto= r) >>>>>>>>>>> { >>>>>>>>>>> - VirtIOPCIProxy *proxy =3D opaque; >>>>>>>>>>> + VirtIOPCIProxy *proxy =3D container_of(d, VirtIOPCIProxy= , pci_dev.qdev); >>>>>>>>>> >>>>>>>>>> Nack. This is going the wrong direction QOM-wise and you among= all >>>>>>>>>> others know that from PCI host bridges! >>>>>>>>> >>>>>>>>> Well, that's just a difference of VIRTIO_PCI_PROXY(d) vs. conta= iner_of. >>>>>>>> >>>>>>>> VIRTIO_PCI_PROXY(d) would be acceptable, sure. But as-is this pa= tch just >>>>>>>> pushes unnecessary work on Fred, me, you or anyone else who work= s with QOM. >>>>>>> >>>>>>> What's VIRTIO_PCI_PROXY? Note this is data path we do not want ex= tra >>>>>>> code. >>>>>> >>>>>> My complaint is the direct access of pci_dev, qdev, etc. parent fi= elds >>>>>> in many places as the main change of this patch. Those mean more p= laces >>>>>> to touch in a future patch. >>>>>> >>>>>> Use of any new-style macro hiding these - wherever the particular = one >>>>>> suggested may be defined or whether it needs to be added - is bett= er. >>>>>> >>>>>> If performance of dynamic_cast is an issue - something I'd leave y= ou to >>>>>> discuss with Anthony - you can just do a C cast directly. Just don= 't >>>>>> spread this qdev paradigm further please. >>>>> >>>>> OK so just >>>>> >>>>> #define VIRTIO_PCI_PROXY(d) container_of(d, VirtIOPCIProxy, pci_dev= .qdev) >>>>> >>>>> is OK with you? >>>> >>>> Well, at least it's better than inlining it... >>>> >>>> I would've expected to see VIRTIO_PCI_PROXY(obj) defined as >>>> OBJECT_CHECK(VirtIOPCIProxy, (obj), TYPE_something) somewhere. >>>> >>>> If, as you imply with "data path", this were a problem, you could ju= st >>>> do VirtIOPCIProxy *proxy =3D (VirtIOPCIProxy *)d inline to allow for >>>> VIRTIO_PCI_PROXY() to be used in the QOM sense elsewhere. >>> >>> I don't get it - where? >>> Since we don't do runtime checks we need container_of - >>> safer than a plain cast. >>> >>> Anyway, when you start doing your QOM conversions it will be >>> easy to do what you like. >> >> I don't get what you don't get >=20 > Wha'ts the QOM way to get virtio pci proxy from > devicestate? > C cast is not what I am looking for. Looking into virtio-pci.c it looks like virtio has a similar deficiency as EHCI USB (my recent series): We lack an abstract intermediate type TYPE_VIRTIO_PCI_PROXY to match the struct VirtIOPCIProxy shared by its subtypes: Object - DeviceState - PCIDevice - VirtIOPCIProxy - virtio-scsi-pci - virtio-rng-pci ... Not sure if that can be extracted from Fred's series already; otherwise I can send you a patch. Then you can do the mentioned: #define VIRTIO_PCI_PROXY(obj) \ OBJECT_CHECK(VirtIOPCIProxy, (obj), TYPE_VIRTIO_PCI_PROXY) DeviceState *dev =3D ...; VirtIOPCIProxy *proxy =3D VIRTIO_PCI_PROXY(dev); where you consider it acceptable performance-wise and a FAST_VIRTIO_PCI_PROXY_FROM_DEVICE(dev) or so elsewhere. Andreas --=20 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imend=F6rffer; HRB 16746 AG N=FCrnbe= rg