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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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