Re: [dpdk-dev] [PATCH v3 15/19] vhost: postpone rings addresses translation

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 10/17/2017 03:24 AM, Yao, Lei A wrote:
> Hi, Maxime
> 
>> -----Original Message-----
>> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
>> Sent: Monday, October 16, 2017 6:48 PM
>> To: Yao, Lei A <lei.a.yao@intel.com>; 'dev@dpdk.org' <dev@dpdk.org>;
>> Horton, Remy <remy.horton@intel.com>; Bie, Tiwei <tiwei.bie@intel.com>;
>> 'yliu@fridaylinux.org' <yliu@fridaylinux.org>
>> Cc: 'mst@redhat.com' <mst@redhat.com>; 'jfreiman@redhat.com'
>> <jfreiman@redhat.com>; 'vkaplans@redhat.com' <vkaplans@redhat.com>;
>> 'jasowang@redhat.com' <jasowang@redhat.com>
>> Subject: Re: [dpdk-dev] [PATCH v3 15/19] vhost: postpone rings addresses
>> translation
>>
>>
>>
>> On 10/16/2017 11:47 AM, Maxime Coquelin wrote:
>>> Hi Yao,
>>>
>>> On 10/16/2017 08:23 AM, Yao, Lei A wrote:
>>>> Hi, Maxime
>>>>
>>>> Add one comment:
>>>> This issue with virtio-net only occur when I use CPU on socket 1.
>>>
>>> Thanks for the report.
>>> I fail to reproduce for now.
>>>
>>> What is your qemu command line?
>>> Is it reproducible systematically when there is a NUMA reallocation
>>> (DPDK on socket 0, QEMU on socket 1)?
>>
>> Nevermind, I just reproduced the (an?) issue.
>> The issue I reproduce is not linked to NUMA reallocation, but to
>> messages sequencing differences between QEMU versions.
>>
>> So, I'm not 100% this is the same issue, as you mention it works fine
>> when using CPU socket 0.
>>
>> The patch "vhost: postpone rings addresses translation" moves rings
>> addresses translation at either vring kick or enable time, depending
>> on whether protocol features are enabled or not. This has been done
>> because we must not interpret ring information as long as the vring is
>> not fully initialized.
>>
>> While my patch works fine with recent QEMU version, it breaks with older
>> ones, like QEMU v2.5. The reason is that on these older versions,
>> VHOST_USER_SET_VRING_ENABLE is called once and before
>> VHOST_USER_SET_VRING_ADDR. At that time, the ring adresses aren't
>> available so the translation is not done. On recent QEMU versions,
>> we receive VHOST_USER_SET_VRING_ENABLE also after having received
>> the rings addresses, so it works fine.
>>
>> The below fix consists in performing the rings addresses translation
>> also when handling VHOST_USER_SET_VRING_ADDR if ring has already been
>> enabled.
>>
>> I'll post a formal patch later today or tomorrow morning after having
>> tested it more conscientiously. Let me know if it fixes your issue.
>>
>> Thanks,
>> Maxime
>>
> Thanks for your quick fix. I try your patch and it can totally work at my side for virtio-net.
> I tested it with Qemu 2.5~2.7, 2.10.
> The previous info about it can work on numa 0 is a misleading info. Because
> I use qemu 2.10 for some special test at that time. So it can work.

Great. Thanks for having tried it.

Maxime

> BRs
> Lei
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index 76c4eeca5..1f6cba4b9 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -372,33 +372,6 @@ ring_addr_to_vva(struct virtio_net *dev, struct
>> vhost_virtqueue *vq,
>>           return qva_to_vva(dev, ra);
>>    }
>>
>> -/*
>> - * The virtio device sends us the desc, used and avail ring addresses.
>> - * This function then converts these to our address space.
>> - */
>> -static int
>> -vhost_user_set_vring_addr(struct virtio_net *dev, VhostUserMsg *msg)
>> -{
>> -       struct vhost_virtqueue *vq;
>> -       struct vhost_vring_addr *addr = &msg->payload.addr;
>> -
>> -       if (dev->mem == NULL)
>> -               return -1;
>> -
>> -       /* addr->index refers to the queue index. The txq 1, rxq is 0. */
>> -       vq = dev->virtqueue[msg->payload.addr.index];
>> -
>> -       /*
>> -        * Rings addresses should not be interpreted as long as the ring
>> is not
>> -        * started and enabled
>> -        */
>> -       memcpy(&vq->ring_addrs, addr, sizeof(*addr));
>> -
>> -       vring_invalidate(dev, vq);
>> -
>> -       return 0;
>> -}
>> -
>>    static struct virtio_net *
>>    translate_ring_addresses(struct virtio_net *dev, int vq_index)
>>    {
>> @@ -464,6 +437,43 @@ translate_ring_addresses(struct virtio_net *dev,
>> int vq_index)
>>    }
>>
>>    /*
>> + * The virtio device sends us the desc, used and avail ring addresses.
>> + * This function then converts these to our address space.
>> + */
>> +static int
>> +vhost_user_set_vring_addr(struct virtio_net **pdev, VhostUserMsg *msg)
>> +{
>> +       struct vhost_virtqueue *vq;
>> +       struct vhost_vring_addr *addr = &msg->payload.addr;
>> +       struct virtio_net *dev = *pdev;
>> +
>> +       if (dev->mem == NULL)
>> +               return -1;
>> +
>> +       /* addr->index refers to the queue index. The txq 1, rxq is 0. */
>> +       vq = dev->virtqueue[msg->payload.addr.index];
>> +
>> +       /*
>> +        * Rings addresses should not be interpreted as long as the ring
>> is not
>> +        * started and enabled
>> +        */
>> +       memcpy(&vq->ring_addrs, addr, sizeof(*addr));
>> +
>> +       vring_invalidate(dev, vq);
>> +
>> +       if (vq->enabled && (dev->features &
>> +                               (1ULL << VHOST_USER_F_PROTOCOL_FEATURES))) {
>> +               dev = translate_ring_addresses(dev,
>> msg->payload.state.index);
>> +               if (!dev)
>> +                       return -1;
>> +
>> +               *pdev = dev;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +/*
>>     * The virtio device sends us the available ring last used index.
>>     */
>>    static int
>> @@ -1273,7 +1283,7 @@ vhost_user_msg_handler(int vid, int fd)
>>                   vhost_user_set_vring_num(dev, &msg);
>>                   break;
>>           case VHOST_USER_SET_VRING_ADDR:
>> -               vhost_user_set_vring_addr(dev, &msg);
>> +               vhost_user_set_vring_addr(&dev, &msg);
>>                   break;
>>           case VHOST_USER_SET_VRING_BASE:
>>                   vhost_user_set_vring_base(dev, &msg);