Re: [Qemu-devel] [PATCH] virtio: set virtio-net/virtio-mmio host features

[Mario Smarduch <m.smarduch@samsung.com>]

Hello,

any feedback on this patch, after a brief email exchange Anthony deferred to
Peter. 

Lack of improper host features handling lowers 1g & 10g performance 
substantially on arm-kvm compared to xeon. 

We would like to have this fixed so we don't have to patch every new release
of qemu, especially virtio stuff.

- Mario

On 02/14/2014 03:49 PM, Peter Maydell wrote:
> CCing the virtio maintainers.
> 
> thanks
> -- PMM
> 
> On 13 February 2014 21:13, Mario Smarduch <m.smarduch@samsung.com> wrote:
>> virtio: set virtio-net/virtio-mmio host features
>>
>> Patch sets 'virtio-net/virtio-mmio' host features to enable network
>> features based on peer capabilities. Currently host features turn
>> of all features by default.
>>
>> Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>
>> ---
>>  hw/virtio/virtio-mmio.c |   29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
>> index 8829eb0..1d940b7 100644
>> --- a/hw/virtio/virtio-mmio.c
>> +++ b/hw/virtio/virtio-mmio.c
>> @@ -23,6 +23,7 @@
>>  #include "hw/virtio/virtio.h"
>>  #include "qemu/host-utils.h"
>>  #include "hw/virtio/virtio-bus.h"
>> +#include "hw/virtio/virtio-net.h"
>>
>>  /* #define DEBUG_VIRTIO_MMIO */
>>
>> @@ -92,6 +93,12 @@ typedef struct {
>>  static void virtio_mmio_bus_new(VirtioBusState *bus, size_t bus_size,
>>                                  VirtIOMMIOProxy *dev);
>>
>> +/* all possible virtio-net features supported */
>> +static Property virtio_mmio_net_properties[] = {
>> +    DEFINE_VIRTIO_NET_FEATURES(VirtIOMMIOProxy, host_features),
>> +    DEFINE_PROP_END_OF_LIST(),
>> +};
>> +
>>  static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
>>  {
>>      VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
>> @@ -347,11 +354,33 @@ static void virtio_mmio_reset(DeviceState *d)
>>
>>  /* virtio-mmio device */
>>
>> +/* Walk virtio-net possible supported features and set host_features, this
>> + * should be done earlier when the object is instantiated but at that point
>> + * you don't know what type of device will be plugged in.
>> + */
>> +static void virtio_mmio_set_net_features(Property *prop, uint32_t *features)
>> +{
>> +    for (; prop && prop->name; prop++) {
>> +        if (prop->defval == true) {
>> +            *features |= (1 << prop->bitnr);
>> +        }  else  {
>> +            *features &= ~(1 << prop->bitnr);
>> +        }
>> +    }
>> +}
>> +
>>  /* This is called by virtio-bus just after the device is plugged. */
>>  static void virtio_mmio_device_plugged(DeviceState *opaque)
>>  {
>>      VirtIOMMIOProxy *proxy = VIRTIO_MMIO(opaque);
>> +    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>> +    Object *obj = OBJECT(vdev);
>>
>> +    /* set host features only for virtio-net */
>> +    if (object_dynamic_cast(obj, TYPE_VIRTIO_NET)) {
>> +        virtio_mmio_set_net_features(virtio_mmio_net_properties,
>> +                                                        &proxy->host_features);
>> +    }
>>      proxy->host_features |= (0x1 << VIRTIO_F_NOTIFY_ON_EMPTY);
>>      proxy->host_features = virtio_bus_get_vdev_features(&proxy->bus,
>>                                                          proxy->host_features);
>> --
>> 1.7.9.5
>>