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Re: [Qemu-devel] [PATCH V2] virtio-net: calculate proper msix vectors on
From: |
Jason Wang |
Subject: |
Re: [Qemu-devel] [PATCH V2] virtio-net: calculate proper msix vectors on init |
Date: |
Tue, 04 Mar 2014 15:41:27 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 |
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.