From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:52364) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDpD1-0007RT-Cc for qemu-devel@nongnu.org; Thu, 07 Mar 2013 23:47:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UDpD0-0004ga-3Y for qemu-devel@nongnu.org; Thu, 07 Mar 2013 23:47:07 -0500 Received: from mail-da0-x232.google.com ([2607:f8b0:400e:c00::232]:64581) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDpCz-0004gD-QY for qemu-devel@nongnu.org; Thu, 07 Mar 2013 23:47:06 -0500 Received: by mail-da0-f50.google.com with SMTP id h15so147271dan.37 for ; Thu, 07 Mar 2013 20:47:03 -0800 (PST) Message-ID: <51396D84.3090404@ozlabs.ru> Date: Fri, 08 Mar 2013 15:48:04 +1100 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <513596D7.3060307@ozlabs.ru> <20130305125614.GA2256@redhat.com> <5135F16B.2010403@ozlabs.ru> <20130305142336.GE2256@redhat.com> <51367864.6080502@ozlabs.ru> <20130306103135.GD16921@redhat.com> In-Reply-To: <20130306103135.GD16921@redhat.com> Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] QEMU -netdev vhost=on + -device virtio-net-pci bug List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: rusty@rustcorp.com.au, "qemu-devel@nongnu.org" , David Gibson Michael, Thanks for the fix. There was another question which was lost in the thread. I am testing virtio-net in two ways: Old -net interface: -net tap,ifname=tap0,script=qemu-ifup.sh \ -net nic,model=virtio,addr=0:0:0 (qemu) info network hub 0 \ virtio-net-pci.0: index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56 \ tap.0: index=0,type=tap,ifname=tap0,script=qemu-ifup.sh,downscript=/etc/qemu-ifdown New -netdev interface: -netdev tap,id=tapnet,ifname=tap0,script=qemu-ifup.sh \ -device virtio-net-pci,netdev=tapnet,addr=0.0 (qemu) info network virtio-net-pci.0: index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56 \ tapnet: index=0,type=tap,ifname=tap0,script=qemu-ifup.sh,downscript=/etc/qemu-ifdown I get very different virtio0 device features and speed (70MB/s vs. 700MB/s). I guess somehow the "hub 0" is responsible but there is no way to avoid it. Is there any way to speed up the virtio-net using the old -net interface? On 06/03/13 21:31, Michael S. Tsirkin wrote: > On Wed, Mar 06, 2013 at 09:57:40AM +1100, Alexey Kardashevskiy wrote: >> On 06/03/13 01:23, Michael S. Tsirkin wrote: >>> On Wed, Mar 06, 2013 at 12:21:47AM +1100, Alexey Kardashevskiy wrote: >>>> On 05/03/13 23:56, Michael S. Tsirkin wrote: >>>>>> The patch f56a12475ff1b8aa61210d08522c3c8aaf0e2648 "vhost: backend >>>>>> masking support" breaks virtio-net + vhost=on on PPC64 platform. >>>>>> >>>>>> The problem command line is: >>>>>> 1) -netdev tap,id=tapnet,ifname=tap0,script=qemu-ifup.sh,vhost=on \ >>>>>> -device virtio-net-pci,netdev=tapnet,addr=0.0 \ >>>>> >>>>> I think the issue is irqfd in not supported on kvm ppc. >>>> >>>> How can I make sure this is the case? Some work has been done there >>>> recently but midnight is quite late to figure this out :) >>> >>> Look in virtio_pci_set_guest_notifiers, what is the >>> value of with_irqfd? >>> bool with_irqfd = msix_enabled(&proxy->pci_dev) && >>> kvm_msi_via_irqfd_enabled(); >>> >>> Also check what each of the values in the expression above is. >> >> Yes, ppc does not have irqfd as kvm_msi_via_irqfd_enabled() returned "false". >> >>>>> Could you please check this: >>>>> >>>>> + /* If guest supports masking, set up irqfd now. >>>>> + * Otherwise, delay until unmasked in the frontend. >>>>> + */ >>>>> + if (proxy->vdev->guest_notifier_mask) { >>>>> + ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector); >>>>> + if (ret < 0) { >>>>> + kvm_virtio_pci_vq_vector_release(proxy, vector); >>>>> + goto undo; >>>>> + } >>>>> + } >>>>> >>>>> >>>>> Could you please add a printf before "undo" and check whether the >>>>> error path above is triggered? >>>> >>>> >>>> Checked, it is not triggered. >>>> >>>> >>>> -- >>>> Alexey >>> >>> I think I get it. >>> Does the following help (probably not the right thing to do, but just >>> for testing): >> >> >> It did not compile (no "queue_no") :) I changed it a bit and now >> vhost=on works fine: >> >> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c >> index a869f53..df1e443 100644 >> --- a/hw/virtio-pci.c >> +++ b/hw/virtio-pci.c >> @@ -798,6 +798,10 @@ static int >> virtio_pci_set_guest_notifiers(DeviceState *d, int nvqs, bool >> assign) >> if (r < 0) { >> goto assign_error; >> } >> + >> + if (!with_irqfd && proxy->vdev->guest_notifier_mask) { >> + proxy->vdev->guest_notifier_mask(proxy->vdev, n, !assign); >> + } >> } >> >> /* Must set vector notifier after guest notifier has been assigned */ >> >> > > I see, OK, the issue is that vhost now starts in a masked state > and no one unmasks it. While the patch will work I think, > it does not benefit from backend masking, the right thing > to do is to add mask notifiers, like what the irqfd path does. > > Will look into this, thanks. > -- Alexey