Re: [Qemu-devel] [ RFC Patch v4 1/3] virtio-net rsc: add a new host offload(rsc) feature bit

[Wei Xu <wexu@redhat.com>]

On 2016年04月05日 16:17, Michael S. Tsirkin wrote:
> On Tue, Apr 05, 2016 at 10:05:17AM +0800, Jason Wang wrote:
>>
>> On 04/04/2016 03:25 AM, wexu@redhat.com wrote:
>>> From: Wei Xu <wexu@redhat.com>
>>>
>>> A new feature bit 'VIRTIO_NET_F_GUEST_RSC' is introduced to support WHQL
>>> Receive-Segment-Offload test, this feature will coalesce tcp packets in
>>> IPv4/6 for userspace virtio-net driver.
>>>
>>> This feature can be enabled either by 'ACK' the feature when loading
>>> the driver in the guest, or by sending the 'VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET'
>>> command to the host via control queue.
>>>
>>> Signed-off-by: Wei Xu <wexu@redhat.com>
>>> ---
>>>   hw/net/virtio-net.c                         | 29 +++++++++++++++++++++++++++--
>>>   include/standard-headers/linux/virtio_net.h |  1 +
>>>   2 files changed, 28 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>>> index 5798f87..bd91a4b 100644
>>> --- a/hw/net/virtio-net.c
>>> +++ b/hw/net/virtio-net.c
>>> @@ -537,6 +537,7 @@ static uint64_t virtio_net_get_features(VirtIODevice *vdev, uint64_t features,
>>>           virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_TSO4);
>>>           virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_TSO6);
>>>           virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_ECN);
>>> +        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_RSC);
>> Several questions here:
>>
>> - I think RSC should work even without vnet_hdr?
That's interesting, but i'm wondering how to test this? could you please 
point me out?
>> - Need we differentiate ipv4 and ipv6 like TSO here?
Sure, thanks.
>> - And looks like this patch should be squash to following patches.
OK.
>>
>>>       }
>>>   
>>>       if (!peer_has_vnet_hdr(n) || !peer_has_ufo(n)) {
>>> @@ -582,7 +583,8 @@ static uint64_t virtio_net_guest_offloads_by_features(uint32_t features)
>>>           (1ULL << VIRTIO_NET_F_GUEST_TSO4) |
>>>           (1ULL << VIRTIO_NET_F_GUEST_TSO6) |
>>>           (1ULL << VIRTIO_NET_F_GUEST_ECN)  |
>>> -        (1ULL << VIRTIO_NET_F_GUEST_UFO);
>>> +        (1ULL << VIRTIO_NET_F_GUEST_UFO)  |
>>> +        (1ULL << VIRTIO_NET_F_GUEST_RSC);
>> Looks like this is unnecessary since we won't set peer offload based on
>> GUEST_RSC.
there is an exclusive check when handling set feature command from 
control queue, so looks it will broke the check if don't include this bit.
>>
>>>   
>>>       return guest_offloads_mask & features;
>>>   }
>>> @@ -1089,7 +1091,8 @@ static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
>>>       return 0;
>>>   }
>>>   
>>> -static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t size)
>>> +static ssize_t virtio_net_do_receive(NetClientState *nc,
>>> +                                     const uint8_t *buf, size_t size)
>>>   {
>>>       VirtIONet *n = qemu_get_nic_opaque(nc);
>>>       VirtIONetQueue *q = virtio_net_get_subqueue(nc);
>>> @@ -1685,6 +1688,26 @@ static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
>>>       return 0;
>>>   }
>>>   
>>> +
>>> +static ssize_t virtio_net_rsc_receive(NetClientState *nc,
>>> +                                      const uint8_t *buf, size_t size)
>>> +{
>>> +    return virtio_net_do_receive(nc, buf, size);
>>> +}
>>> +
>>> +static ssize_t virtio_net_receive(NetClientState *nc,
>>> +                                  const uint8_t *buf, size_t size)
>>> +{
>>> +    VirtIONet *n;
>>> +
>>> +    n = qemu_get_nic_opaque(nc);
>>> +    if (n->curr_guest_offloads & VIRTIO_NET_F_GUEST_RSC) {
>>> +        return virtio_net_rsc_receive(nc, buf, size);
>>> +    } else {
>>> +        return virtio_net_do_receive(nc, buf, size);
>>> +    }
>>> +}
>> The changes here looks odd since it did nothing. Like I've mentioned,
>> better merge the patch into following ones.
OK.
>>
>>> +
>>>   static NetClientInfo net_virtio_info = {
>>>       .type = NET_CLIENT_OPTIONS_KIND_NIC,
>>>       .size = sizeof(NICState),
>>> @@ -1909,6 +1932,8 @@ static Property virtio_net_properties[] = {
>>>                          TX_TIMER_INTERVAL),
>>>       DEFINE_PROP_INT32("x-txburst", VirtIONet, net_conf.txburst, TX_BURST),
>>>       DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx),
>>> +    DEFINE_PROP_BIT("guest_rsc", VirtIONet, host_features,
>>> +                    VIRTIO_NET_F_GUEST_RSC, true),
>> Need to compat the bit for old machine type to unbreak migration I believe?
> And definitely disable by default.
There maybe some windows specific details about this, i'll discuss with 
Yan and update.
>
>> Btw, also need a patch for virtio spec.
Sure.
>>
>> Thanks
>>
>>>       DEFINE_PROP_END_OF_LIST(),
>>>   };
>>>   
>>> diff --git a/include/standard-headers/linux/virtio_net.h b/include/standard-headers/linux/virtio_net.h
>>> index a78f33e..5b95762 100644
>>> --- a/include/standard-headers/linux/virtio_net.h
>>> +++ b/include/standard-headers/linux/virtio_net.h
>>> @@ -55,6 +55,7 @@
>>>   #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
>>>   					 * Steering */
>>>   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
>>> +#define VIRTIO_NET_F_GUEST_RSC  24      /* Guest can coalesce tcp packets */
>>>   
>>>   #ifndef VIRTIO_NET_NO_LEGACY
>>>   #define VIRTIO_NET_F_GSO	6	/* Host handles pkts w/ any GSO type */