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Re: [Qemu-devel] [PATCH V2] virtio-net: calculate proper msix vectors on
From: |
Gonglei |
Subject: |
Re: [Qemu-devel] [PATCH V2] virtio-net: calculate proper msix vectors on init |
Date: |
Tue, 4 Mar 2014 19:18:35 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1 |
On 2014/3/4 15:41, Jason Wang wrote:
> On 03/04/2014 11:26 AM, Gonglei (Arei) wrote:
>>> -----Original Message-----
>>> From: address@hidden
>>> [mailto:address@hidden On
>>> Behalf Of Jason Wang
>>> Sent: Friday, February 21, 2014 5:05 PM
>>> To: address@hidden; address@hidden; address@hidden
>>> Cc: Paolo Bonzini; Jason Wang
>>> Subject: [Qemu-devel] [PATCH V2] virtio-net: calculate proper msix vectors
>>> on
>>> init
>>>
>>> Currently, the default msix vectors for virtio-net-pci is 3 which is
>>> obvious not suitable for multiqueue guest, so we depends on the user
>>> or management tools to pass a correct vectors parameter. In fact, we
>>> can simplifying this by calculate the number of vectors on init.
>>>
>>> Consider we have N queues, the number of vectors needed is 2*N + 2
>>> (plus one config interrupt and control vq). We didn't check whether or
>>> not host support control vq because it was added unconditionally by
>>> qemu to avoid breaking legacy guests such as Minix.
>>>
>>> Cc: Paolo Bonzini <address@hidden>
>>> Cc: Michael S. Tsirkin <address@hidden>
>>> Signed-off-by: Jason Wang <address@hidden>
>>> ---
>>> hw/virtio/virtio-pci.c | 8 +++++++-
>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>>> index 7b91841..3b3b0e2 100644
>>> --- a/hw/virtio/virtio-pci.c
>>> +++ b/hw/virtio/virtio-pci.c
>>> @@ -1416,7 +1416,8 @@ static const TypeInfo virtio_serial_pci_info = {
>>> static Property virtio_net_properties[] = {
>>> DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
>>> VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, false),
>>> - DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 3),
>>> + DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
>>> + DEV_NVECTORS_UNSPECIFIED),
>>> DEFINE_VIRTIO_NET_FEATURES(VirtIOPCIProxy, host_features),
>>> DEFINE_NIC_PROPERTIES(VirtIONetPCI, vdev.nic_conf),
>>> DEFINE_VIRTIO_NET_PROPERTIES(VirtIONetPCI, vdev.net_conf),
>>> @@ -1428,6 +1429,11 @@ static int virtio_net_pci_init(VirtIOPCIProxy
>>> *vpci_dev)
>>> DeviceState *qdev = DEVICE(vpci_dev);
>>> VirtIONetPCI *dev = VIRTIO_NET_PCI(vpci_dev);
>>> DeviceState *vdev = DEVICE(&dev->vdev);
>>> + VirtIONet *net = VIRTIO_NET(&dev->vdev);
>>> +
>>> + if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
>>> + vpci_dev->nvectors = 2 * MAX(net->nic_conf.queues, 1) + 2;
>>> + }
>>>
>>> virtio_net_set_config_size(&dev->vdev, vpci_dev->host_features);
>>> virtio_net_set_netclient_name(&dev->vdev, qdev->id,
>>> --
>>> 1.8.3.2
>>>
>> Good catch.
>>
>> Reviewed-by: Gonglei <address@hidden>
>>
>>
>> Best regards,
>> -Gonglei
>>
>
> Hi Gonglei:
>
> Thanks for the reviewing. Looks like this patch has a bug which will
> break the migration if "vectors=" is not specified.
>
> Will post a new version.
>
Yes, you are right, Jason.
You need to add backwards-compatibility properties in hw/pc.h
Best regards,
-Gonglei