Message-ID: <CACGkMEsEZMhS0zSRY0XviXSmDALd2zons0nAk43DTCBu_iA5tw@mail.gmail.com>
Date:   Mon, 16 Jan 2023 10:55:58 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Gautam Dawar <gdawar@....com>
Cc:     Gautam Dawar <gautam.dawar@....com>, linux-net-drivers@....com,
        netdev@...r.kernel.org, eperezma@...hat.com, tanuj.kamde@....com,
        Koushik.Dutta@....com, harpreet.anand@....com,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 08/11] sfc: implement device status related vdpa
 config operations

On Fri, Jan 13, 2023 at 2:33 PM Gautam Dawar <gdawar@....com> wrote:
>
>
> On 1/13/23 11:50, Jason Wang wrote:
> > Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> >
> >
> > On Fri, Jan 13, 2023 at 2:11 PM Gautam Dawar <gdawar@....com> wrote:
> >>
> >> On 1/13/23 09:58, Jason Wang wrote:
> >>> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> >>>
> >>>
> >>> On Wed, Jan 11, 2023 at 2:36 PM Jason Wang <jasowang@...hat.com> wrote:
> >>>> On Mon, Jan 9, 2023 at 6:21 PM Gautam Dawar <gdawar@....com> wrote:
> >>>>> On 12/14/22 12:15, Jason Wang wrote:
> >>>>>> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> >>>>>>
> >>>>>>
> >>>>>> On Wed, Dec 7, 2022 at 10:57 PM Gautam Dawar <gautam.dawar@....com> wrote:
> >>>>>>> vDPA config opertions to handle get/set device status and device
> >>>>>>> reset have been implemented.
> >>>>>>>
> >>>>>>> Signed-off-by: Gautam Dawar <gautam.dawar@....com>
> >>>>>>> ---
> >>>>>>>     drivers/net/ethernet/sfc/ef100_vdpa.c     |   7 +-
> >>>>>>>     drivers/net/ethernet/sfc/ef100_vdpa.h     |   1 +
> >>>>>>>     drivers/net/ethernet/sfc/ef100_vdpa_ops.c | 133 ++++++++++++++++++++++
> >>>>>>>     3 files changed, 140 insertions(+), 1 deletion(-)
> >>>>>>>
> >>>>>>> diff --git a/drivers/net/ethernet/sfc/ef100_vdpa.c b/drivers/net/ethernet/sfc/ef100_vdpa.c
> >>>>>>> index 04d64bfe3c93..80bca281a748 100644
> >>>>>>> --- a/drivers/net/ethernet/sfc/ef100_vdpa.c
> >>>>>>> +++ b/drivers/net/ethernet/sfc/ef100_vdpa.c
> >>>>>>> @@ -225,9 +225,14 @@ static int vdpa_allocate_vis(struct efx_nic *efx, unsigned int *allocated_vis)
> >>>>>>>
> >>>>>>>     static void ef100_vdpa_delete(struct efx_nic *efx)
> >>>>>>>     {
> >>>>>>> +       struct vdpa_device *vdpa_dev;
> >>>>>>> +
> >>>>>>>            if (efx->vdpa_nic) {
> >>>>>>> +               vdpa_dev = &efx->vdpa_nic->vdpa_dev;
> >>>>>>> +               ef100_vdpa_reset(vdpa_dev);
> >>>>>> Any reason we need to reset during delete?
> >>>>> ef100_reset_vdpa_device() does the necessary clean-up including freeing
> >>>>> irqs, deleting filters and deleting the vrings which is required while
> >>>>> removing the vdpa device or unloading the driver.
> >>>> That's fine but the name might be a little bit confusing since vDPA
> >>>> reset is not necessary here.
> >>>>
> >>>>>>> +
> >>>>>>>                    /* replace with _vdpa_unregister_device later */
> >>>>>>> -               put_device(&efx->vdpa_nic->vdpa_dev.dev);
> >>>>>>> +               put_device(&vdpa_dev->dev);
> >>>>>>>                    efx->vdpa_nic = NULL;
> >>>>>>>            }
> >>>>>>>            efx_mcdi_free_vis(efx);
> >>>>>>> diff --git a/drivers/net/ethernet/sfc/ef100_vdpa.h b/drivers/net/ethernet/sfc/ef100_vdpa.h
> >>>>>>> index a33edd6dda12..1b0bbba88154 100644
> >>>>>>> --- a/drivers/net/ethernet/sfc/ef100_vdpa.h
> >>>>>>> +++ b/drivers/net/ethernet/sfc/ef100_vdpa.h
> >>>>>>> @@ -186,6 +186,7 @@ int ef100_vdpa_add_filter(struct ef100_vdpa_nic *vdpa_nic,
> >>>>>>>                              enum ef100_vdpa_mac_filter_type type);
> >>>>>>>     int ef100_vdpa_irq_vectors_alloc(struct pci_dev *pci_dev, u16 nvqs);
> >>>>>>>     void ef100_vdpa_irq_vectors_free(void *data);
> >>>>>>> +int ef100_vdpa_reset(struct vdpa_device *vdev);
> >>>>>>>
> >>>>>>>     static inline bool efx_vdpa_is_little_endian(struct ef100_vdpa_nic *vdpa_nic)
> >>>>>>>     {
> >>>>>>> diff --git a/drivers/net/ethernet/sfc/ef100_vdpa_ops.c b/drivers/net/ethernet/sfc/ef100_vdpa_ops.c
> >>>>>>> index 132ddb4a647b..718b67f6da90 100644
> >>>>>>> --- a/drivers/net/ethernet/sfc/ef100_vdpa_ops.c
> >>>>>>> +++ b/drivers/net/ethernet/sfc/ef100_vdpa_ops.c
> >>>>>>> @@ -251,6 +251,62 @@ static bool is_qid_invalid(struct ef100_vdpa_nic *vdpa_nic, u16 idx,
> >>>>>>>            return false;
> >>>>>>>     }
> >>>>>>>
> >>>>>>> +static void ef100_reset_vdpa_device(struct ef100_vdpa_nic *vdpa_nic)
> >>>>>>> +{
> >>>>>>> +       int i;
> >>>>>>> +
> >>>>>>> +       WARN_ON(!mutex_is_locked(&vdpa_nic->lock));
> >>>>>>> +
> >>>>>>> +       if (!vdpa_nic->status)
> >>>>>>> +               return;
> >>>>>>> +
> >>>>>>> +       vdpa_nic->vdpa_state = EF100_VDPA_STATE_INITIALIZED;
> >>>>>>> +       vdpa_nic->status = 0;
> >>>>>>> +       vdpa_nic->features = 0;
> >>>>>>> +       for (i = 0; i < (vdpa_nic->max_queue_pairs * 2); i++)
> >>>>>>> +               reset_vring(vdpa_nic, i);
> >>>>>>> +}
> >>>>>>> +
> >>>>>>> +/* May be called under the rtnl lock */
> >>>>>>> +int ef100_vdpa_reset(struct vdpa_device *vdev)
> >>>>>>> +{
> >>>>>>> +       struct ef100_vdpa_nic *vdpa_nic = get_vdpa_nic(vdev);
> >>>>>>> +
> >>>>>>> +       /* vdpa device can be deleted anytime but the bar_config
> >>>>>>> +        * could still be vdpa and hence efx->state would be STATE_VDPA.
> >>>>>>> +        * Accordingly, ensure vdpa device exists before reset handling
> >>>>>>> +        */
> >>>>>>> +       if (!vdpa_nic)
> >>>>>>> +               return -ENODEV;
> >>>>>>> +
> >>>>>>> +       mutex_lock(&vdpa_nic->lock);
> >>>>>>> +       ef100_reset_vdpa_device(vdpa_nic);
> >>>>>>> +       mutex_unlock(&vdpa_nic->lock);
> >>>>>>> +       return 0;
> >>>>>>> +}
> >>>>>>> +
> >>>>>>> +static int start_vdpa_device(struct ef100_vdpa_nic *vdpa_nic)
> >>>>>>> +{
> >>>>>>> +       int rc = 0;
> >>>>>>> +       int i, j;
> >>>>>>> +
> >>>>>>> +       for (i = 0; i < (vdpa_nic->max_queue_pairs * 2); i++) {
> >>>>>>> +               if (can_create_vring(vdpa_nic, i)) {
> >>>>>>> +                       rc = create_vring(vdpa_nic, i);
> >>>>>> So I think we can safely remove the create_vring() in set_vq_ready()
> >>>>>> since it's undefined behaviour if set_vq_ready() is called after
> >>>>>> DRIVER_OK.
> >>>>> Is this (undefined) behavior documented in the virtio spec?
> >>>> This part is kind of tricky:
> >>>>
> >>>> PCI transport has a queue_enable field. And recently,
> >>>> VIRTIO_F_RING_RESET was introduced. Let's start without that first:
> >>>>
> >>>> In
> >>>>
> >>>> 4.1.4.3.2 Driver Requirements: Common configuration structure layout
> >>>>
> >>>> It said:
> >>>>
> >>>> "The driver MUST configure the other virtqueue fields before enabling
> >>>> the virtqueue with queue_enable."
> >>>>
> >>>> and
> >>>>
> >>>> "The driver MUST NOT write a 0 to queue_enable."
> >>>>
> >>>> My understanding is that:
> >>>>
> >>>> 1) Write 0 is forbidden
> >>>> 2) Write 1 after DRIVER_OK is undefined behaviour (or need to clarify)
> >>>>
> >>>> With VIRTIO_F_RING_RESET is negotiated:
> >>>>
> >>>> "
> >>>> If VIRTIO_F_RING_RESET has been negotiated, after the driver writes 1
> >>>> to queue_reset to reset the queue, the driver MUST NOT consider queue
> >>>> reset to be complete until it reads back 0 in queue_reset. The driver
> >>>> MAY re-enable the queue by writing 1 to queue_enable after ensuring
> >>>> that other virtqueue fields have been set up correctly. The driver MAY
> >>>> set driver-writeable queue configuration values to different values
> >>>> than those that were used before the queue reset. (see 2.6.1).
> >>>> "
> >>>>
> >>>> Write 1 to queue_enable after DRIVER_OK and after the queue is reset is allowed.
> >>>>
> >>>> Thanks
> >>> Btw, I just realized that we need to stick to the current behaviour,
> >>> that is to say, to allow set_vq_ready() to be called after DRIVER_OK.
> >> So, both set_vq_ready() and DRIVER_OK are required for vring creation
> >> and their order doesn't matter. Is that correct?
> > Yes.
> >
> >> Also, will set_vq_ready(0) after DRIVER_OK result in queue deletion?
> > I think it should be treated as suspended or stopped. Since the device
> > should survive from kicking the vq even if the driver does
> > set_vq_ready(0).
> Ok. Is it expected that a queue restart (set_vq_ready(0) followed by
> set_vq_ready(1)) will start the queue from the last queue configuration
> when VIRTIO_F_RING_RESET isn't negotiated?

I think it's better to have this.

Thanks

> >
> > Thanks
> >
> >>> It is needed for the cvq trap and migration for control virtqueue:
> >>>
> >>> https://www.mail-archive.com/qemu-devel@nongnu.org/msg931491.html
> >>>
> >>> Thanks
> >>>
> >>>
> >>>>> If so, can
> >>>>> you please point me to the section of virtio spec that calls this order
> >>>>> (set_vq_ready() after setting DRIVER_OK) undefined? Is it just that the
> >>>>> queue can't be enabled after DRIVER_OK or the reverse (disabling the
> >>>>> queue) after DRIVER_OK is not allowed?
> >>>>>>> +                       if (rc)
> >>>>>>> +                               goto clear_vring;
> >>>>>>> +               }
> >>>>>>> +       }
> >>>>>>> +       vdpa_nic->vdpa_state = EF100_VDPA_STATE_STARTED;
> >>>>>>> +       return rc;
> >>>>>>> +
> >>>>>>> +clear_vring:
> >>>>>>> +       for (j = 0; j < i; j++)
> >>>>>>> +               if (vdpa_nic->vring[j].vring_created)
> >>>>>>> +                       delete_vring(vdpa_nic, j);
> >>>>>>> +       return rc;
> >>>>>>> +}
> >>>>>>> +
> >>>>>>>     static int ef100_vdpa_set_vq_address(struct vdpa_device *vdev,
> >>>>>>>                                         u16 idx, u64 desc_area, u64 driver_area,
> >>>>>>>                                         u64 device_area)
> >>>>>>> @@ -568,6 +624,80 @@ static u32 ef100_vdpa_get_vendor_id(struct vdpa_device *vdev)
> >>>>>>>            return EF100_VDPA_VENDOR_ID;
> >>>>>>>     }
> >>>>>>>
> >>>>>>> +static u8 ef100_vdpa_get_status(struct vdpa_device *vdev)
> >>>>>>> +{
> >>>>>>> +       struct ef100_vdpa_nic *vdpa_nic = get_vdpa_nic(vdev);
> >>>>>>> +       u8 status;
> >>>>>>> +
> >>>>>>> +       mutex_lock(&vdpa_nic->lock);
> >>>>>>> +       status = vdpa_nic->status;
> >>>>>>> +       mutex_unlock(&vdpa_nic->lock);
> >>>>>>> +       return status;
> >>>>>>> +}
> >>>>>>> +
> >>>>>>> +static void ef100_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> >>>>>>> +{
> >>>>>>> +       struct ef100_vdpa_nic *vdpa_nic = get_vdpa_nic(vdev);
> >>>>>>> +       u8 new_status;
> >>>>>>> +       int rc;
> >>>>>>> +
> >>>>>>> +       mutex_lock(&vdpa_nic->lock);
> >>>>>>> +       if (!status) {
> >>>>>>> +               dev_info(&vdev->dev,
> >>>>>>> +                        "%s: Status received is 0. Device reset being done\n",
> >>>>>>> +                        __func__);
> >>>>>>> +               ef100_reset_vdpa_device(vdpa_nic);
> >>>>>>> +               goto unlock_return;
> >>>>>>> +       }
> >>>>>>> +       new_status = status & ~vdpa_nic->status;
> >>>>>>> +       if (new_status == 0) {
> >>>>>>> +               dev_info(&vdev->dev,
> >>>>>>> +                        "%s: New status same as current status\n", __func__);
> >>>>>>> +               goto unlock_return;
> >>>>>>> +       }
> >>>>>>> +       if (new_status & VIRTIO_CONFIG_S_FAILED) {
> >>>>>>> +               ef100_reset_vdpa_device(vdpa_nic);
> >>>>>>> +               goto unlock_return;
> >>>>>>> +       }
> >>>>>>> +
> >>>>>>> +       if (new_status & VIRTIO_CONFIG_S_ACKNOWLEDGE &&
> >>>>>>> +           vdpa_nic->vdpa_state == EF100_VDPA_STATE_INITIALIZED) {
> >>>>>> As replied before, I think there's no need to check
> >>>>>> EF100_VDPA_STATE_INITIALIZED, otherwise it could be a bug somewhere.
> >>>>> Ok. Will remove the check against EF100_VDPA_STATE_INITIALIZED.
> >>>>>>> +               vdpa_nic->status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
> >>>>>>> +               new_status &= ~VIRTIO_CONFIG_S_ACKNOWLEDGE;
> >>>>>>> +       }
> >>>>>>> +       if (new_status & VIRTIO_CONFIG_S_DRIVER &&
> >>>>>>> +           vdpa_nic->vdpa_state == EF100_VDPA_STATE_INITIALIZED) {
> >>>>>>> +               vdpa_nic->status |= VIRTIO_CONFIG_S_DRIVER;
> >>>>>>> +               new_status &= ~VIRTIO_CONFIG_S_DRIVER;
> >>>>>>> +       }
> >>>>>>> +       if (new_status & VIRTIO_CONFIG_S_FEATURES_OK &&
> >>>>>>> +           vdpa_nic->vdpa_state == EF100_VDPA_STATE_INITIALIZED) {
> >>>>>>> +               vdpa_nic->status |= VIRTIO_CONFIG_S_FEATURES_OK;
> >>>>>>> +               vdpa_nic->vdpa_state = EF100_VDPA_STATE_NEGOTIATED;
> >>>>>> I think we can simply map EF100_VDPA_STATE_NEGOTIATED to
> >>>>>> VIRTIO_CONFIG_S_FEATURES_OK.
> >>>>>>
> >>>>>> E.g the code doesn't fail the feature negotiation by clearing the
> >>>>>> VIRTIO_CONFIG_S_FEATURES_OK when ef100_vdpa_set_driver_feature fails?
> >>>>> Ok.
> >>>>>> Thanks
> >>>>> Regards,
> >>>>>
> >>>>> Gautam
> >>>>>
>

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