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Date: Fri, 21 Jun 2024 11:03:01 -0700
From: Joe Damato <jdamato@...tly.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: "Nambiar, Amritha" <amritha.nambiar@...el.com>,
Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
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>,
"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 Mon, Apr 15, 2024 at 09:37:09AM -0700, Tony Nguyen wrote:
>
>
> On 4/13/2024 12:24 PM, Joe Damato wrote:
> > On Thu, Apr 11, 2024 at 04:02:37PM -0700, Nambiar, Amritha wrote:
> > > 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.
> >
> > Based on the findings of I40E_SUSPENDED below, the above if statement is
> > still slightly incorrect, please see below.
> >
> > > > > > +}
> > > > > > +
> > > > > > /**
> > > > > > * 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.
> >
> > Thanks for the thorough review; I appreciate your insight. The more I look
> > at the i40e code paths, the more I realize that it is much trickier than I
> > originally thought.
> >
> > > > 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 .
> >
> > Here's what I see in this path, namely that i40e_suspend does not call
> > i40e_queue_set_napi but sets appropriate bits that can be checked.
> >
> > i40e_suspend:
> > __I40E_DOWN is set
> > __I40E_SUSPENDED is set
> > rtnl_lock
> > i40e_clear_interrupt_scheme
> > i40e_vsi_free_q_vectors
> > i40e_free_q_vector
> > rtnl_unlock
> >
> > It seems in the suspend case the i40e_free_rx_resources and
> > i40e_free_tx_resources are not called. This means I probably missed a case
> > and need to call i40e_queue_set_napi to set the NAPI mapping to NULL
> > somewhere in here without calling it twice. See further below for my
> > thoughts on this.
> >
> > Continuing with resume, though:
> >
> > i40e_resume:
> > rtnl_lock
> > i40e_restore_interrupt_scheme
> > i40e_vsi_alloc_q_vectors
> > i40e_vsi_alloc_q_vector
> > __I40E_DOWN is cleared
> > i40e_reset_and_rebuild (passes lock_acquired = true)
> > i40e_rebuild (passes locked_acquired = true)
> > rtnl_unlock
> > __I40E_SUSPENDED is cleared
> >
> > So, in this case i40e_resume would want to to call __i40e_queue_set_napi
> > with locked = true, to avoid rtnl since it's already been taken. I think to
> > cover this case __I40E_SUSPENDED needs to be checked but true can be passed
> > to the helper to avoid taking rtnl in the helper.
> >
> > This is an adjusted if statement, which is likely still incorrect in some
> > cases (especially when considering my comments below on the
> > i40e_free_[rt]x_resource paths), but maybe getting slightly closer:
> >
> > /* __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.
> > *
> > * __I40E_SUSPENDED is set in i40e_suspend and cleared in i40e_resume
> > * after rtnl_lock + i40_rebuild (with lock_acquired = true). In
> > * i40e_resume's call to i40e_rebuild, rtnl is held so
> > * __i40e_queue_set_napi should not take the lock, either.
> > *
> > * __I40E_IN_REMOVE is set in i40e_remove, and freeing the tx/rx
> > * resources will trigger this path. In this case, rtnl will not be held,
> > * so locked=false must be passed to the helper.
> > *
> > * __I40E_DOWN is set in a few places: i40e_probe, i40e_remove,
> > * i40e_shutdown, i40e_suspend. It is only cleared in i40e_probe after
> > * the vsi_open path is taken (in this case rtnl is needed) and it is
> > * cleared in i40e_resume, where RTNL is not needed, but the i40e_resume
> > * case is handled by checking __I40E_SUSPENDED in the first if block.
> > */
> > 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) |
> > test_bit(__I40E_SUSPENDED, pf->state))
> > __i40e_queue_set_napi(vsi->netdev, queue_index, type, napi,
> > true);
> > else if (test_bit(__I40E_IN_REMOVE, pf->state) ||
> > test_bit(__I40E_DOWN, 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);
> >
> >
> > But please see below about i40e_free_q_vector.
> >
> > > > > > 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);
> >
> > It appears to me that some cases may not end up calling
> > i40e_free_tx_resources or i40e_free_rx_resources, but most (or all?) cases
> > do call i40e_free_q_vector which is where the NAPI is deleted.
> >
> > It probably makes more sense to put the NULL setting where the NAPI delete
> > happens, and then check those paths to see where rtnl is taken and make
> > sure the bit checking in the if statement lines up properly.
> >
> > Before I go any deeper down this rabbit hole, I'll wait to see what the
> > i40e maintainers say / think about this.
>
> + Alex for input
Just wanted to follow up on this; would really appreciate any
insight or advice you all can give me before I try posting another
version.
We'd really love to have support for these APIs in i40e, because we
have a lot of machines with this NIC in our fleet.
Thanks,
Joe
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