On 2023/5/18 14:12, Jason Wang wrote:
> On Thu, May 18, 2023 at 2:00 PM Eugenio Perez Martin
> <epere...@redhat.com> wrote:
>>
>> On Thu, May 18, 2023 at 7:47 AM Jason Wang <jasow...@redhat.com> wrote:
>>>
>>> On Wed, May 17, 2023 at 11:02 PM Hawkins Jiawei <yin31...@gmail.com> wrote:
>>>>
>>>> Sorry for forgetting cc when replying to the email.
>>>>
>>>> On Wed, 17 May 2023 at 16:22, Eugenio Perez Martin <epere...@redhat.com>
>>>> wrote:
>>>>>
>>>>> On Wed, May 17, 2023 at 7:22 AM Jason Wang <jasow...@redhat.com> wrote:
>>>>>>
>>>>>> On Sat, May 6, 2023 at 10:07 PM Hawkins Jiawei <yin31...@gmail.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> This patch introduces the vhost_vdpa_net_cvq_add() and
>>>>>>> refactors the vhost_vdpa_net_load*(), so that QEMU can
>>>>>>> send CVQ state load commands in parallel.
>>>>>>>
>>>>>>> To be more specific, this patch introduces vhost_vdpa_net_cvq_add()
>>>>>>> to add SVQ control commands to SVQ and kick the device,
>>>>>>> but does not poll the device used buffers. QEMU will not
>>>>>>> poll and check the device used buffers in vhost_vdpa_net_load()
>>>>>>> until all CVQ state load commands have been sent to the device.
>>>>>>>
>>>>>>> What's more, in order to avoid buffer overwriting caused by
>>>>>>> using `svq->cvq_cmd_out_buffer` and `svq->status` as the
>>>>>>> buffer for all CVQ state load commands when sending
>>>>>>> CVQ state load commands in parallel, this patch introduces
>>>>>>> `out_cursor` and `in_cursor` in vhost_vdpa_net_load(),
>>>>>>> pointing to the available buffer for in descriptor and
>>>>>>> out descriptor, so that different CVQ state load commands can
>>>>>>> use their unique buffer.
>>>>>>>
>>>>>>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1578
>>>>>>> Signed-off-by: Hawkins Jiawei <yin31...@gmail.com>
>>>>>>> ---
>>>>>>> net/vhost-vdpa.c | 152 +++++++++++++++++++++++++++++++++++++----------
>>>>>>> 1 file changed, 120 insertions(+), 32 deletions(-)
>>>>>>>
>>>>>>> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
>>>>>>> index 10804c7200..14e31ca5c5 100644
>>>>>>> --- a/net/vhost-vdpa.c
>>>>>>> +++ b/net/vhost-vdpa.c
>>>>>>> @@ -590,6 +590,44 @@ static void vhost_vdpa_net_cvq_stop(NetClientState
>>>>>>> *nc)
>>>>>>> vhost_vdpa_net_client_stop(nc);
>>>>>>> }
>>>>>>>
>>>>>>> +/**
>>>>>>> + * vhost_vdpa_net_cvq_add() adds SVQ control commands to SVQ,
>>>>>>> + * kicks the device but does not poll the device used buffers.
>>>>>>> + *
>>>>>>> + * Return the number of elements added to SVQ if success.
>>>>>>> + */
>>>>>>> +static int vhost_vdpa_net_cvq_add(VhostVDPAState *s,
>>>>>>> + void **out_cursor, size_t out_len,
>>>>>>
>>>>>> Can we track things like cursors in e.g VhostVDPAState ?
>>>>>>
>>>>>
>>>>> Cursors will only be used at device startup. After that, cursors are
>>>>> always the full buffer. Do we want to "pollute" VhostVDPAState with
>>>>> things that will not be used after the startup?
>>>
>>> So it's the cursor of the cvq_cmd_out_buffer, it would be more elegant
>>> to keep it with where the cvq_cmd_out_buffer is placed. It can avoid
>>> passing cursors in several levels.
>>> >>
>> That's right, there is no reason to update at vhost_vdpa_net_cvq_add.
>> It can be done at the caller.
But in any case, these cursors need to be passed as alone parameters to
vhost_vdpa_net_cvq_add(), so that they can be accessed for
`struct iovec` `iov_base` field, right? Considering that
we always pass these parameters, so I also update them together in
vhost_vdpa_net_cvq_add() in this patch.
If we want to avoid passing cursors in several levels, is it okay
to backup `cvq_cmd_out_buffer` and `status` in vhost_vdpa_net_load(),
access and update them through `VhostVDPAState` directly during loading,
and restore them when finishing loading.
>>
>>> Or it would be even better to have some buffer allocation helpers to
>>> alloc and free in and out buffers.
>>>
>>
>> I think that's overkill, as the buffers are always the in and out CVQ
>> buffers. They are allocated at qemu initialization, and mapped /
>> unmapped at device start / stop for now.
>
> It's not a must, we can do it if it has more users for sure.
>
>>
>> To manage them dynamically would need code to map them at any time etc.
>
> Thanks
>
>>
>> Thanks!
>>
>>> Thanks
>>>
>>>>>
>>>>> Maybe we can create a struct for them and then pass just this struct?
>>>>
>>>> Yes, Currently, the new version of vhost_vdpa_net_cvq_add() is only
>>>> called in vhost_vdpa_net_load() at startup, so these cursors will not be
>>>> used after startup.
>>>>
>>>> If needed, we can create a `VhostVDPACursor` as suggested by Eugenio.
>>>>
>>>>>
>>>>> Thanks!
>>>>>
>>>>>>> + virtio_net_ctrl_ack **in_cursor,
>>>>>>> size_t in_len)
>>>>>>> +{
>>>>>>> + /* Buffers for the device */
>>>>>>> + const struct iovec out = {
>>>>>>> + .iov_base = *out_cursor,
>>>>>>> + .iov_len = out_len,
>>>>>>> + };
>>>>>>> + const struct iovec in = {
>>>>>>> + .iov_base = *in_cursor,
>>>>>>> + .iov_len = sizeof(virtio_net_ctrl_ack),
>>>>>>> + };
>>>>>>> + VhostShadowVirtqueue *svq =
>>>>>>> g_ptr_array_index(s->vhost_vdpa.shadow_vqs, 0);
>>>>>>> + int r;
>>>>>>> +
>>>>>>> + r = vhost_svq_add(svq, &out, 1, &in, 1, NULL);
>>>>>>> + if (unlikely(r != 0)) {
>>>>>>> + if (unlikely(r == -ENOSPC)) {
>>>>>>> + qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device
>>>>>>> queue\n",
>>>>>>> + __func__);
>>>>>>> + }
>>>>>>> + return r;
>>>>>>> + }
>>>>>>> +
>>>>>>> + /* Update the cursor */
>>>>>>> + *out_cursor += out_len;
>>>>>>> + *in_cursor += 1;
>>>>>>> +
>>>>>>> + return 1;
>>>>>>> +}
>>>>>>> +
>>>>>>> /**
>>>>>>> * vhost_vdpa_net_cvq_add_and_wait() adds SVQ control commands to SVQ,
>>>>>>> * kicks the device and polls the device used buffers.
>>>>>>> @@ -628,69 +666,82 @@ static ssize_t
>>>>>>> vhost_vdpa_net_cvq_add_and_wait(VhostVDPAState *s,
>>>>>>> return vhost_svq_poll(svq);
>>>>>>> }
>>>>>>>
>>>>>>> -static ssize_t vhost_vdpa_net_load_cmd(VhostVDPAState *s, uint8_t
>>>>>>> class,
>>>>>>> - uint8_t cmd, const void *data,
>>>>>>> - size_t data_size)
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * vhost_vdpa_net_load_cmd() restores the NIC state through SVQ.
>>>>>>> + *
>>>>>>> + * Return the number of elements added to SVQ if success.
>>>>>>> + */
>>>>>>> +static int vhost_vdpa_net_load_cmd(VhostVDPAState *s,
>>>>>>> + void **out_cursor, uint8_t class,
>>>>>>> uint8_t cmd,
>>>>>>> + const void *data, size_t data_size,
>>>>>>> + virtio_net_ctrl_ack **in_cursor)
>>>>>>> {
>>>>>>> const struct virtio_net_ctrl_hdr ctrl = {
>>>>>>> .class = class,
>>>>>>> .cmd = cmd,
>>>>>>> };
>>>>>>>
>>>>>>> - assert(data_size < vhost_vdpa_net_cvq_cmd_page_len() -
>>>>>>> sizeof(ctrl));
>>>>>>> + assert(sizeof(ctrl) < vhost_vdpa_net_cvq_cmd_page_len() -
>>>>>>> + (*out_cursor - s->cvq_cmd_out_buffer));
>>>>>>> + assert(data_size < vhost_vdpa_net_cvq_cmd_page_len() -
>>>>>>> sizeof(ctrl) -
>>>>>>> + (*out_cursor - s->cvq_cmd_out_buffer));
>>>>>>>
>>>>>>> - memcpy(s->cvq_cmd_out_buffer, &ctrl, sizeof(ctrl));
>>>>>>> - memcpy(s->cvq_cmd_out_buffer + sizeof(ctrl), data, data_size);
>>>>>>> + memcpy(*out_cursor, &ctrl, sizeof(ctrl));
>>>>>>> + memcpy(*out_cursor + sizeof(ctrl), data, data_size);
>>>>>>>
>>>>>>> - return vhost_vdpa_net_cvq_add_and_wait(s, sizeof(ctrl) + data_size,
>>>>>>> - sizeof(virtio_net_ctrl_ack));
>>>>>>> + return vhost_vdpa_net_cvq_add(s, out_cursor, sizeof(ctrl) +
>>>>>>> data_size,
>>>>>>> + in_cursor,
>>>>>>> sizeof(virtio_net_ctrl_ack));
>>>>>>> }
>>>>>>>
>>>>>>> -static int vhost_vdpa_net_load_mac(VhostVDPAState *s, const VirtIONet
>>>>>>> *n)
>>>>>>> +/**
>>>>>>> + * vhost_vdpa_net_load_mac() restores the NIC mac through SVQ.
>>>>>>> + *
>>>>>>> + * Return the number of elements added to SVQ if success.
>>>>>>> + */
>>>>>>> +static int vhost_vdpa_net_load_mac(VhostVDPAState *s, const VirtIONet
>>>>>>> *n,
>>>>>>> + void **out_cursor, virtio_net_ctrl_ack
>>>>>>> **in_cursor)
>>>>>>> {
>>>>>>> uint64_t features = n->parent_obj.guest_features;
>>>>>>> if (features & BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR)) {
>>>>>>> - ssize_t dev_written = vhost_vdpa_net_load_cmd(s,
>>>>>>> VIRTIO_NET_CTRL_MAC,
>>>>>>> -
>>>>>>> VIRTIO_NET_CTRL_MAC_ADDR_SET,
>>>>>>> - n->mac,
>>>>>>> sizeof(n->mac));
>>>>>>> - if (unlikely(dev_written < 0)) {
>>>>>>> - return dev_written;
>>>>>>> - }
>>>>>>> -
>>>>>>> - return *s->status != VIRTIO_NET_OK;
>>>>>>> + return vhost_vdpa_net_load_cmd(s, out_cursor,
>>>>>>> VIRTIO_NET_CTRL_MAC,
>>>>>>> + VIRTIO_NET_CTRL_MAC_ADDR_SET,
>>>>>>> + n->mac, sizeof(n->mac),
>>>>>>> in_cursor);
>>>>>>> }
>>>>>>>
>>>>>>> return 0;
>>>>>>> }
>>>>>>>
>>>>>>> -static int vhost_vdpa_net_load_mq(VhostVDPAState *s,
>>>>>>> - const VirtIONet *n)
>>>>>>> +/**
>>>>>>> + * vhost_vdpa_net_load_mac() restores the NIC mq state through SVQ.
>>>>>>> + *
>>>>>>> + * Return the number of elements added to SVQ if success.
>>>>>>> + */
>>>>>>> +static int vhost_vdpa_net_load_mq(VhostVDPAState *s, const VirtIONet
>>>>>>> *n,
>>>>>>> + void **out_cursor, virtio_net_ctrl_ack
>>>>>>> **in_cursor)
>>>>>>> {
>>>>>>> struct virtio_net_ctrl_mq mq;
>>>>>>> uint64_t features = n->parent_obj.guest_features;
>>>>>>> - ssize_t dev_written;
>>>>>>>
>>>>>>> if (!(features & BIT_ULL(VIRTIO_NET_F_MQ))) {
>>>>>>> return 0;
>>>>>>> }
>>>>>>>
>>>>>>> mq.virtqueue_pairs = cpu_to_le16(n->curr_queue_pairs);
>>>>>>> - dev_written = vhost_vdpa_net_load_cmd(s, VIRTIO_NET_CTRL_MQ,
>>>>>>> -
>>>>>>> VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &mq,
>>>>>>> - sizeof(mq));
>>>>>>> - if (unlikely(dev_written < 0)) {
>>>>>>> - return dev_written;
>>>>>>> - }
>>>>>>> -
>>>>>>> - return *s->status != VIRTIO_NET_OK;
>>>>>>> + return vhost_vdpa_net_load_cmd(s, out_cursor, VIRTIO_NET_CTRL_MQ,
>>>>>>> + VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET,
>>>>>>> + &mq, sizeof(mq), in_cursor);
>>>>>>> }
>>>>>>>
>>>>>>> static int vhost_vdpa_net_load(NetClientState *nc)
>>>>>>> {
>>>>>>> VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
>>>>>>> + VhostShadowVirtqueue *svq;
>>>>>>> + void *out_cursor;
>>>>>>> + virtio_net_ctrl_ack *in_cursor;
>>>>>>> struct vhost_vdpa *v = &s->vhost_vdpa;
>>>>>>> const VirtIONet *n;
>>>>>>> - int r;
>>>>>>> + ssize_t cmds_in_flight = 0, dev_written, r;
>>>>>>>
>>>>>>> assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>>>>>>>
>>>>>>> @@ -699,14 +750,51 @@ static int vhost_vdpa_net_load(NetClientState *nc)
>>>>>>> }
>>>>>>>
>>>>>>> n = VIRTIO_NET(v->dev->vdev);
>>>>>>> - r = vhost_vdpa_net_load_mac(s, n);
>>>>>>> + out_cursor = s->cvq_cmd_out_buffer;
>>>>>>> + in_cursor = s->status;
>>>>>>> +
>>>>>>> + r = vhost_vdpa_net_load_mac(s, n, &out_cursor, &in_cursor);
>>>>>>> if (unlikely(r < 0))
>>>>>>> return r;
>>>>>>> }
>>>>>>> - r = vhost_vdpa_net_load_mq(s, n);
>>>>>>> - if (unlikely(r)) {
>>>>>>> + cmds_in_flight += r;
>>>>>>> +
>>>>>>> + r = vhost_vdpa_net_load_mq(s, n, &out_cursor, &in_cursor);
>>>>>>> + if (unlikely(r < 0)) {
>>>>>>> return r;
>>>>>>> }
>>>>>>> + cmds_in_flight += r;
>>>>>>> +
>>>>>>> + /* Poll for all used buffer from device */
>>>>>>> + svq = g_ptr_array_index(s->vhost_vdpa.shadow_vqs, 0);
>>>>>>> + while (cmds_in_flight > 0) {
>>>>>>> + /*
>>>>>>> + * We can poll here since we've had BQL from the time we sent
>>>>>>> the
>>>>>>> + * descriptor. Also, we need to take the answer before SVQ
>>>>>>> pulls
>>>>>>> + * by itself, when BQL is released
>>>>>>> + */
>>>>>>> + dev_written = vhost_svq_poll(svq);
>>>>>>
>>>>>> I'd tweak vhost_svq_poll to accept cmds_in_flight.
>>>>
>>>> That sounds great!
>>>> I will refactor the code here and send the v2 patch after
>>>> your patch.
>>>>
>>>> Thanks!
>>>>
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>>> +
>>>>>>> + if (unlikely(!dev_written)) {
>>>>>>> + /*
>>>>>>> + * vhost_svq_poll() return 0 when something wrong, such as
>>>>>>> + * QEMU waits for too long time or no available used buffer
>>>>>>> + * from device, and there is no need to continue polling
>>>>>>> + * in this case.
>>>>>>> + */
>>>>>>> + return -EINVAL;
>>>>>>> + }
>>>>>>> +
>>>>>>> + --cmds_in_flight;
>>>>>>> + }
>>>>>>> +
>>>>>>> + /* Check the buffers written by device */
>>>>>>> + for (virtio_net_ctrl_ack *status = s->status; status < in_cursor;
>>>>>>> + ++status) {
>>>>>>> + if (*status != VIRTIO_NET_OK) {
>>>>>>> + return -EINVAL;
>>>>>>> + }
>>>>>>> + }
>>>>>>>
>>>>>>> return 0;
>>>>>>> }
>>>>>>> --
>>>>>>> 2.25.1
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
