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SubjectRe: [PATCH net-next 08/11] sfc: implement device status related vdpa config operations
On Wed, Jan 11, 2023 at 2:36 PM Jason Wang <jasowang@redhat.com> wrote:
>
> On Mon, Jan 9, 2023 at 6:21 PM Gautam Dawar <gdawar@amd.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@amd.com> wrote:
> > >> vDPA config opertions to handle get/set device status and device
> > >> reset have been implemented.
> > >>
> > >> Signed-off-by: Gautam Dawar <gautam.dawar@amd.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.

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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