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Message-ID: <f6a3f010-8fb5-4494-9ef0-23501ea01f64@intel.com>
Date: Thu, 11 Apr 2024 16:02:37 -0700
From: "Nambiar, Amritha" <amritha.nambiar@...el.com>
To: Joe Damato <jdamato@...tly.com>
CC: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
<intel-wired-lan@...ts.osuosl.org>, <sridhar.samudrala@...el.com>,
<nalramli@...tly.com>, Jesse Brandeburg <jesse.brandeburg@...el.com>, "Tony
Nguyen" <anthony.l.nguyen@...el.com>, "David S. Miller"
<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
<kuba@...nel.org>, "Paolo Abeni" <pabeni@...hat.com>
Subject: Re: [intel-next 1/2] net/i40e: link NAPI instances to queues and IRQs
On 4/10/2024 4:43 PM, Joe Damato wrote:
> On Wed, Apr 10, 2024 at 02:10:52AM -0700, Nambiar, Amritha wrote:
>> On 4/9/2024 9:39 PM, Joe Damato wrote:
>>> Make i40e compatible with the newly added netlink queue GET APIs.
>>>
>>> $ ./cli.py --spec ../../../Documentation/netlink/specs/netdev.yaml \
>>> --do queue-get --json '{"ifindex": 3, "id": 1, "type": "rx"}'
>>>
>>> {'id': 1, 'ifindex': 3, 'napi-id': 162, 'type': 'rx'}
>>>
>>> $ ./cli.py --spec ../../../Documentation/netlink/specs/netdev.yaml \
>>> --do napi-get --json '{"id": 162}'
>>>
>>> {'id': 162, 'ifindex': 3, 'irq': 136}
>>>
>>> The above output suggests that irq 136 was allocated for queue 1, which has
>>> a NAPI ID of 162.
>>>
>>> To double check this is correct, the IRQ to queue mapping can be verified
>>> by checking /proc/interrupts:
>>>
>>> $ cat /proc/interrupts | grep 136\: | \
>>> awk '{print "irq: " $1 " name " $76}'
>>>
>>> irq: 136: name i40e-vlan300-TxRx-1
>>>
>>> Suggests that queue 1 has IRQ 136, as expected.
>>>
>>> Signed-off-by: Joe Damato <jdamato@...tly.com>
>>> ---
>>> drivers/net/ethernet/intel/i40e/i40e.h | 2 +
>>> drivers/net/ethernet/intel/i40e/i40e_main.c | 58 +++++++++++++++++++++
>>> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 4 ++
>>> 3 files changed, 64 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
>>> index 2fbabcdb5bb5..5900ed5c7170 100644
>>> --- a/drivers/net/ethernet/intel/i40e/i40e.h
>>> +++ b/drivers/net/ethernet/intel/i40e/i40e.h
>>> @@ -1267,6 +1267,8 @@ int i40e_ioctl(struct net_device *netdev, struct ifreq *ifr, int cmd);
>>> int i40e_open(struct net_device *netdev);
>>> int i40e_close(struct net_device *netdev);
>>> int i40e_vsi_open(struct i40e_vsi *vsi);
>>> +void i40e_queue_set_napi(struct i40e_vsi *vsi, unsigned int queue_index,
>>> + enum netdev_queue_type type, struct napi_struct *napi);
>>> void i40e_vlan_stripping_disable(struct i40e_vsi *vsi);
>>> int i40e_add_vlan_all_mac(struct i40e_vsi *vsi, s16 vid);
>>> int i40e_vsi_add_vlan(struct i40e_vsi *vsi, u16 vid);
>>> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
>>> index 0bdcdea0be3e..6384a0c73a05 100644
>>> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
>>> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
>>> @@ -3448,6 +3448,58 @@ static struct xsk_buff_pool *i40e_xsk_pool(struct i40e_ring *ring)
>>> return xsk_get_pool_from_qid(ring->vsi->netdev, qid);
>>> }
>>> +/**
>>> + * __i40e_queue_set_napi - Set the napi instance for the queue
>>> + * @dev: device to which NAPI and queue belong
>>> + * @queue_index: Index of queue
>>> + * @type: queue type as RX or TX
>>> + * @napi: NAPI context
>>> + * @locked: is the rtnl_lock already held
>>> + *
>>> + * Set the napi instance for the queue. Caller indicates the lock status.
>>> + */
>>> +static void
>>> +__i40e_queue_set_napi(struct net_device *dev, unsigned int queue_index,
>>> + enum netdev_queue_type type, struct napi_struct *napi,
>>> + bool locked)
>>> +{
>>> + if (!locked)
>>> + rtnl_lock();
>>> + netif_queue_set_napi(dev, queue_index, type, napi);
>>> + if (!locked)
>>> + rtnl_unlock();
>>> +}
>>> +
>>> +/**
>>> + * i40e_queue_set_napi - Set the napi instance for the queue
>>> + * @vsi: VSI being configured
>>> + * @queue_index: Index of queue
>>> + * @type: queue type as RX or TX
>>> + * @napi: NAPI context
>>> + *
>>> + * Set the napi instance for the queue. The rtnl lock state is derived from the
>>> + * execution path.
>>> + */
>>> +void
>>> +i40e_queue_set_napi(struct i40e_vsi *vsi, unsigned int queue_index,
>>> + enum netdev_queue_type type, struct napi_struct *napi)
>>> +{
>>> + struct i40e_pf *pf = vsi->back;
>>> +
>>> + if (!vsi->netdev)
>>> + return;
>>> +
>>> + if (current_work() == &pf->service_task ||
>>> + test_bit(__I40E_PF_RESET_REQUESTED, pf->state) ||
>>
>> I think we might need something like ICE_PREPARED_FOR_RESET which detects
>> all kinds of resets(PFR/CORE/GLOBR). __I40E_PF_RESET_REQUESTED handles PFR
>> only. So, this might assert for RTNL lock on CORER/GLOBR.
>
> The i40e code is a bit tricky so I'm not sure about these cases. Here's
> what it looks like to me, but hopefully Intel can weigh-in here as well.
>
> As some one who is not an expert in i40e, what follows is a guess that is
> likely wrong ;)
>
> The __I40E_GLOBAL_RESET_REQUESTED case it looks to me (I could totally
> be wrong here) that the i40e_reset_subtask calls i40e_rebuild with
> lock_acquired = false. In this case, we want __i40e_queue_set_napi to
> pass locked = true (because i40e_rebuild will acquire the lock for us).
>
> The __I40E_CORE_RESET_REQUESTED case appears to be the same as the
> __I40E_GLOBAL_RESET_REQUESTED case in that i40e_rebuild is called with
> lock_acquired = false meaning we also want __i40e_queue_set_napi to pass
> locked = true (because i40e_rebuild will acquire the lock for us).
>
> __I40E_PF_RESET_REQUESTED is more complex.
>
> It seems:
> When the __I40E_PF_RESET_REQUESTED bit is set in:
> - i40e_handle_lldp_event
> - i40e_tx_timeout
> - i40e_intr
> - i40e_resume_port_tx
> - i40e_suspend_port_tx
> - i40e_hw_dcb_config
>
> then: i40e_service_event_schedule is called which queues
> i40e_service_task, which calls i40e_reset_subtask, which
> clears the __I40E_PF_RESET_REQUESTED bit and calls
> i40e_do_reset passing lock_acquired = false. In the
> __I40E_PF_RESET_REQUESTED case, i40e_reset_and_rebuild
> called with lock_acquired = false again and passed through to
> i40e_rebuild which will take rtnl on its own. This means
> in these cases, __i40e_queue_set_napi can pass locked = true.
>
> However...
>
> - i40e_set_features
> - i40e_ndo_bridge_setlink
> - i40e_create_queue_channel
> - i40e_configure_queue_channels
> - Error case in i40e_vsi_open
>
> call i40e_do_reset directly and pass lock_acquired = true so
> i40e_reset_and_rebuild will not take the RTNL.
>
> Important assumption: I assume that passing lock_acquired = true
> means that the lock really was previously acquired (and not simply
> unnecessary and not taken ?).
>
> If that is correct, then __i40e_queue_set_napi should also not take the rtnl (e.g.
> locked = true).
>
> Again, I could be totally off here, but it looks like when:
>
> (current_work() == &pf->service_task) && test_bit(__I40E_PF_RESET_REQUESTED, pf->state)
>
> is true, we want to call __i40e_queue_set_napi with locked = true,
>
> and also all the other cases we want __i40e_queue_set_napi with locked = true
>
>>> + test_bit(__I40E_DOWN, pf->state) ||
>>> + test_bit(__I40E_SUSPENDED, pf->state))
>>> + __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
>>> + false);
>>> + else
>>> + __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
>>> + true);
>
> I *think* (but honestly... I have no idea) the correct if statement *might* be
> something like:
>
> /* __I40E_PF_RESET_REQUESTED via the service_task will
> * call i40e_rebuild with lock_acquired = false, causing rtnl to be
> * taken, meaning __i40e_queue_set_napi should *NOT* take the lock.
> *
> * __I40E_PF_RESET_REQUESTED when set directly and not via the
> * service task, i40e_reset is called with lock_acquired = true,
> * implying that the rtnl was already taken (and, more
> * specifically, the lock was not simply unnecessary and skipped)
> * and so __i40e_queue_set_napi should *NOT* take the lock.
> *
> * __I40E_GLOBAL_RESET_REQUESTED and __I40E_CORE_RESET_REQUESTED
> * trigger the service_task (via i40e_intr) which will cause
> * i40e_rebuild to acquire rtnl and so __i40e_queue_set_napi should
> * not acquire it.
> */
> if (current_work() == &pf->service_task ||
> test_bit(__I40E_PF_RESET_REQUESTED, pf->state) ||
> test_bit(__I40E_GLOBAL_RESET_REQUESTED, pf->state) ||
> test_bit(__I40E_CORE_RESET_REQUESTED, pf->state))
> __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
> true);
> else if (test_bit(__I40E_DOWN, pf->state) ||
> test_bit(__I40E_SUSPENDED, pf->state))
> __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
> false);
> else
> __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
> true);
>
> I suppose to figure this out, I'd need to investigate all cases where
> i40e_rebuild is called with lock_acquired = true to ensure that the lock was
> actually acquired (and not just unnecessary).
>
> Unless some one who knows about i40e can answer this question more
> definitively.
>
I'll wait for the i40e maintainers to chime in here.
>>> +}
>>> +
>>> /**
>>> * i40e_configure_tx_ring - Configure a transmit ring context and rest
>>> * @ring: The Tx ring to configure
>>> @@ -3558,6 +3610,8 @@ static int i40e_configure_tx_ring(struct i40e_ring *ring)
>>> /* cache tail off for easier writes later */
>>> ring->tail = hw->hw_addr + I40E_QTX_TAIL(pf_q);
>>> + i40e_queue_set_napi(vsi, ring->queue_index, NETDEV_QUEUE_TYPE_TX,
>>> + &ring->q_vector->napi);
>>
>> I am not sure very sure of this, have you tested this for the reset/rebuild
>> path as well (example: ethtool -L and change queues). Just wondering if this
>> path is taken for first time VSI init or additionally for any VSI rebuilds
>> as well.
>
> Can you explain more about what your concern is? I'm not sure I follow.
> Was the concern just that on rebuild this code path might not be
> executed because the driver might take a different path?
>
> If so, I traced the code (and tested with ethtool):
>
> When the device is probed:
>
> i40e_probe
> i40e_vsi_open
> i40e_vsi_configure
> i40e_vsi_configure_rx
> i40e_configure_rx_ring
> i40e_vsi_configure_tx
> i40e_configure_tx_ring
>
> When you use ethtool to change the channel count:
>
> i40e_set_channels
> i40e_reconfig_rss_queues
> i40e_reset_and_rebuild
> i40e_rebuild
> i40e_pf_unquiesce_all_vsi
> i40e_unquiesce_vsi
> i40e_vsi_open
> [.. the call stack above for i40e_vsi_open ..]
>
> Are those the two paths you had in mind or were there other ones? FWIW, using
> ethtool to change the channel count followed by using the cli.py returns what
> appears to be correct data, so I think the ethtool -L case is covered.
>
Yes, this is what I had mind. Good to know that it is covered.
> Let me know if I am missing any cases you had in mind or if this answers your
> question.
>
One other case was the suspend/resume callback. This path involves
remapping vectors and rings (just like rebuild after changing channels),
If this takes the i40e_rebuild path like before, then we are covered, as
your changes are in i40e_vsi_configure. If not, we'll have to add it
after re-initializing interrupt scheme .
>>> return 0;
>>> }
>>> @@ -3716,6 +3770,8 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
>>> ring->queue_index, pf_q);
>>> }
>>> + i40e_queue_set_napi(vsi, ring->queue_index, NETDEV_QUEUE_TYPE_RX,
>>> + &ring->q_vector->napi);
>>>
>> Same as above.
>>
>> return 0;
>>> }
>>> @@ -4178,6 +4234,8 @@ static int i40e_vsi_request_irq_msix(struct i40e_vsi *vsi, char *basename)
>>> q_vector->affinity_notify.notify = i40e_irq_affinity_notify;
>>> q_vector->affinity_notify.release = i40e_irq_affinity_release;
>>> irq_set_affinity_notifier(irq_num, &q_vector->affinity_notify);
>>> + netif_napi_set_irq(&q_vector->napi, q_vector->irq_num);
>>> +
>>> /* Spread affinity hints out across online CPUs.
>>> *
>>> * get_cpu_mask returns a static constant mask with
>>> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> index 64d198ed166b..d380885ff26d 100644
>>> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> @@ -821,6 +821,8 @@ void i40e_clean_tx_ring(struct i40e_ring *tx_ring)
>>> void i40e_free_tx_resources(struct i40e_ring *tx_ring)
>>> {
>>> i40e_clean_tx_ring(tx_ring);
>>> + i40e_queue_set_napi(tx_ring->vsi, tx_ring->queue_index,
>>> + NETDEV_QUEUE_TYPE_TX, NULL);
>>> kfree(tx_ring->tx_bi);
>>> tx_ring->tx_bi = NULL;
>>> @@ -1526,6 +1528,8 @@ void i40e_clean_rx_ring(struct i40e_ring *rx_ring)
>>> void i40e_free_rx_resources(struct i40e_ring *rx_ring)
>>> {
>>> i40e_clean_rx_ring(rx_ring);
>>> + i40e_queue_set_napi(rx_ring->vsi, rx_ring->queue_index,
>>> + NETDEV_QUEUE_TYPE_RX, NULL);
>>> if (rx_ring->vsi->type == I40E_VSI_MAIN)
>>> xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
>>> rx_ring->xdp_prog = NULL;
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