virtio-rng-pci: Allow setting nvectors, so we can use MSI-X

[PATCH] virtio-rng-pci: Allow setting nvectors, so we can use MSI-X

Posted by Philippe Mathieu-Daudé 3 years, 3 months ago

From: David Daney <david.daney@fungible.com>

Most other virtio-pci devices allow MSI-X, let's have it for rng too.

Signed-off-by: David Daney <david.daney@fungible.com>
Reviewed-by: Marcin Nowakowski <marcin.nowakowski@fungible.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@fungible.com>
---
 hw/virtio/virtio-rng-pci.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/hw/virtio/virtio-rng-pci.c b/hw/virtio/virtio-rng-pci.c
index 151ece6f94..6e76f8b57b 100644
--- a/hw/virtio/virtio-rng-pci.c
+++ b/hw/virtio/virtio-rng-pci.c
@@ -13,6 +13,7 @@
 
 #include "hw/virtio/virtio-pci.h"
 #include "hw/virtio/virtio-rng.h"
+#include "hw/qdev-properties.h"
 #include "qapi/error.h"
 #include "qemu/module.h"
 #include "qom/object.h"
@@ -31,11 +32,23 @@ struct VirtIORngPCI {
     VirtIORNG vdev;
 };
 
+static Property virtio_rng_properties[] = {
+    DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
+                    VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
+    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
+                       DEV_NVECTORS_UNSPECIFIED),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void virtio_rng_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
 {
     VirtIORngPCI *vrng = VIRTIO_RNG_PCI(vpci_dev);
     DeviceState *vdev = DEVICE(&vrng->vdev);
 
+    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
+        vpci_dev->nvectors = 2;
+    }
+
     if (!qdev_realize(vdev, BUS(&vpci_dev->bus), errp)) {
         return;
     }
@@ -54,6 +67,7 @@ static void virtio_rng_pci_class_init(ObjectClass *klass, void *data)
     pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_RNG;
     pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
     pcidev_k->class_id = PCI_CLASS_OTHERS;
+    device_class_set_props(dc, virtio_rng_properties);
 }
 
 static void virtio_rng_initfn(Object *obj)
-- 
2.37.3

Re: [PATCH] virtio-rng-pci: Allow setting nvectors, so we can use MSI-X

Posted by Stefan Hajnoczi 3 years, 3 months ago

On Fri, 14 Oct 2022 at 12:10, Philippe Mathieu-Daudé
<philmd@fungible.com> wrote:
>
> From: David Daney <david.daney@fungible.com>
>
> Most other virtio-pci devices allow MSI-X, let's have it for rng too.
>
> Signed-off-by: David Daney <david.daney@fungible.com>
> Reviewed-by: Marcin Nowakowski <marcin.nowakowski@fungible.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@fungible.com>
> ---
>  hw/virtio/virtio-rng-pci.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/hw/virtio/virtio-rng-pci.c b/hw/virtio/virtio-rng-pci.c
> index 151ece6f94..6e76f8b57b 100644
> --- a/hw/virtio/virtio-rng-pci.c
> +++ b/hw/virtio/virtio-rng-pci.c
> @@ -13,6 +13,7 @@
>
>  #include "hw/virtio/virtio-pci.h"
>  #include "hw/virtio/virtio-rng.h"
> +#include "hw/qdev-properties.h"
>  #include "qapi/error.h"
>  #include "qemu/module.h"
>  #include "qom/object.h"
> @@ -31,11 +32,23 @@ struct VirtIORngPCI {
>      VirtIORNG vdev;
>  };
>
> +static Property virtio_rng_properties[] = {
> +    DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
> +                    VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),

ioeventfd is unrelated to MSI-X. It controls whether the virtqueue
kick is handled in the vCPU thread (ioctl(KVM_RUN) exit) or the main
loop thread (KVM ioeventfd).

I took a quick look at virtio-rng.c to see if there is anything that
doesn't work in the main loop. It looks okay to me but consider
dropping this line to minimize the risk of breaking something.

> +    DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
> +                       DEV_NVECTORS_UNSPECIFIED),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
>  static void virtio_rng_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>  {
>      VirtIORngPCI *vrng = VIRTIO_RNG_PCI(vpci_dev);
>      DeviceState *vdev = DEVICE(&vrng->vdev);
>
> +    if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> +        vpci_dev->nvectors = 2;

Checked against the spec: 1 configuration change notification and 1
virtqueue used buffer notification = 2 MSI-X vectors.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

> +     }
> +
>      if (!qdev_realize(vdev, BUS(&vpci_dev->bus), errp)) {
>          return;
>      }
> @@ -54,6 +67,7 @@ static void virtio_rng_pci_class_init(ObjectClass *klass, void *data)
>      pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_RNG;
>      pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
>      pcidev_k->class_id = PCI_CLASS_OTHERS;
> +    device_class_set_props(dc, virtio_rng_properties);
>  }
>
>  static void virtio_rng_initfn(Object *obj)
> --
> 2.37.3
>
>