Re: [PATCH v1 1/2] virtio-mem-pci: Allow setting nvectors, so we can use MSI-X

[Thomas Huth]

On 27/01/2025 15.28, David Hildenbrand wrote:
> Let's do it similar as virtio-balloon-pci. With this change, we can
> use virtio-mem-pci on s390x, although plugging will still fail until
> properly wired up in the machine.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>   hw/core/machine.c          |  3 +++
>   hw/virtio/virtio-mem-pci.c | 12 ++++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 8f396ef803..5e1d9e12ef 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -41,6 +41,9 @@ GlobalProperty hw_compat_9_2[] = {
>       { "virtio-balloon-pci", "vectors", "0" },
>       { "virtio-balloon-pci-transitional", "vectors", "0" },
>       { "virtio-balloon-pci-non-transitional", "vectors", "0" },
> +    { "virtio-mem-pci", "vectors", "0" },
> +    { "virtio-mem-pci-transitional", "vectors", "0" },
> +    { "virtio-mem-pci-non-transitional", "vectors", "0" },

 Hi!

Do we need the entries fo the -transitional and -non-transitional devices? 
Since virtio-mem is rather new, I would expect that those should not exist 
here? E.g. virtio-balloon-pci.c has:

    .transitional_name     = "virtio-balloon-pci-transitional",
    .non_transitional_name = "virtio-balloon-pci-non-transitional",

but there are no such entries in virtio-mem-pci.c ... ?

 Thomas


>   };
>   const size_t hw_compat_9_2_len = G_N_ELEMENTS(hw_compat_9_2);
>   
> diff --git a/hw/virtio/virtio-mem-pci.c b/hw/virtio/virtio-mem-pci.c
> index 1b4e9a3284..6cc5f0fd3b 100644
> --- a/hw/virtio/virtio-mem-pci.c
> +++ b/hw/virtio/virtio-mem-pci.c
> @@ -22,6 +22,10 @@ static void virtio_mem_pci_realize(VirtIOPCIProxy *vpci_dev, 
> Error **errp)
>       VirtIOMEMPCI *mem_pci = VIRTIO_MEM_PCI(vpci_dev);
>       DeviceState *vdev = DEVICE(&mem_pci->vdev);
>   
> +    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> +        vpci_dev->nvectors = 2;
> +    }
> +
>       virtio_pci_force_virtio_1(vpci_dev);
>       qdev_realize(vdev, BUS(&vpci_dev->bus), errp);
>   }
> @@ -152,6 +156,13 @@ static void virtio_mem_pci_set_requested_size(Object *obj, 
> Visitor *v,
>       object_property_set(OBJECT(&pci_mem->vdev), name, v, errp);
>   }
>   
> +static const Property virtio_mem_pci_class_properties[] = {
> +    DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
> +                    VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> +    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
> +                       DEV_NVECTORS_UNSPECIFIED),
> +};
> +
>   static void virtio_mem_pci_class_init(ObjectClass *klass, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -164,6 +175,7 @@ static void virtio_mem_pci_class_init(ObjectClass *klass, 
> void *data)
>       set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>       pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
>       pcidev_k->class_id = PCI_CLASS_OTHERS;
> +    device_class_set_props(dc, virtio_mem_pci_class_properties);
>   
>       mdc->get_addr = virtio_mem_pci_get_addr;
>       mdc->set_addr = virtio_mem_pci_set_addr;