Re: [Qemu-devel] [PATCH] virtio-blk: enable multiple vectors when using multiple I/O queues

[Paolo Bonzini]

On 01/02/2018 06:51, Changpeng Liu wrote:
> Currently virtio-pci driver hardcoded 2 vectors for virtio-blk device,
> for multiple I/O queues scenario, all the I/O queues will share one
> interrupt vector, while here, enable multiple vectors according to
> the number of I/O queues.
> 
> Signed-off-by: Changpeng Liu <address@hidden>

This is a change in the device's interface to the guest ("guest ABI"),
so it has to be protected with migration compatibility: just add to
HW_COMPAT_2_11 in include/hw/compat.h the following:

    {\
        .driver   = "virtio-blk-pci",\
        .property = "vectors",\
        .value    = "2",\
    },\
    {\
        .driver   = "vhost-user-blk-pci",\
        .property = "vectors",\
        .value    = "2",\
    },\

Otherwise, it looks good.

Thanks,

Paolo

> ---
>  hw/virtio/virtio-pci.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 9ae10f0..379b00c 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1932,7 +1932,7 @@ static Property virtio_blk_pci_properties[] = {
>      DEFINE_PROP_UINT32("class", VirtIOPCIProxy, class_code, 0),
>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
>                      VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> -    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
> +    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 
> DEV_NVECTORS_UNSPECIFIED),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -1941,6 +1941,10 @@ static void virtio_blk_pci_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>      VirtIOBlkPCI *dev = VIRTIO_BLK_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
>  
> +    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> +        vpci_dev->nvectors = dev->vdev.conf.num_queues + 1;
> +    }
> +
>      qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
>      object_property_set_bool(OBJECT(vdev), true, "realized", errp);
>  }
> @@ -1983,7 +1987,7 @@ static const TypeInfo virtio_blk_pci_info = {
>  
>  static Property vhost_user_blk_pci_properties[] = {
>      DEFINE_PROP_UINT32("class", VirtIOPCIProxy, class_code, 0),
> -    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
> +    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 
> DEV_NVECTORS_UNSPECIFIED),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -1992,6 +1996,10 @@ static void vhost_user_blk_pci_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>      VHostUserBlkPCI *dev = VHOST_USER_BLK_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&dev->vdev);
>  
> +    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> +        vpci_dev->nvectors = dev->vdev.num_queues + 1;
> +    }
> +
>      qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
>      object_property_set_bool(OBJECT(vdev), true, "realized", errp);
>  }
>