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Message-ID: <da52a255-e92c-48ac-bb30-02df2e86f119@linux.dev>
Date: Fri, 10 May 2024 21:33:46 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Andy Gospodarek <andrew.gospodarek@...adcom.com>
Cc: Ajit Khaparde <ajit.khaparde@...adcom.com>, Wei Huang
<wei.huang2@....com>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
netdev@...r.kernel.org, bhelgaas@...gle.com, corbet@....net,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, alex.williamson@...hat.com, michael.chan@...adcom.com,
manoj.panicker2@....com, Eric.VanTassell@....com
Subject: Re: [PATCH V1 8/9] bnxt_en: Add TPH support in BNXT driver
On 10/05/2024 16:23, Andy Gospodarek wrote:
> On Fri, May 10, 2024 at 11:35:35AM +0100, Vadim Fedorenko wrote:
>> On 10.05.2024 04:55, Ajit Khaparde wrote:
>>> On Thu, May 9, 2024 at 2:50 PM Vadim Fedorenko
>>> <vadim.fedorenko@...ux.dev> wrote:
>>>>
>>>> On 09/05/2024 17:27, Wei Huang wrote:
>>>>> From: Manoj Panicker <manoj.panicker2@....com>
>>>>>
>>>>> As a usage example, this patch implements TPH support in Broadcom BNXT
>>>>> device driver by invoking pcie_tph_set_st() function when interrupt
>>>>> affinity is changed.
>>>>>
>>>>> Reviewed-by: Ajit Khaparde <ajit.khaparde@...adcom.com>
>>>>> Reviewed-by: Andy Gospodarek <andrew.gospodarek@...adcom.com>
>>>>> Reviewed-by: Wei Huang <wei.huang2@....com>
>>>>> Signed-off-by: Manoj Panicker <manoj.panicker2@....com>
>>>>> ---
>>>>> drivers/net/ethernet/broadcom/bnxt/bnxt.c | 51 +++++++++++++++++++++++
>>>>> drivers/net/ethernet/broadcom/bnxt/bnxt.h | 4 ++
>>>>> 2 files changed, 55 insertions(+)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>>>>> index 2c2ee79c4d77..be9c17566fb4 100644
>>>>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>>>>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>>>>> @@ -55,6 +55,7 @@
>>>>> #include <net/page_pool/helpers.h>
>>>>> #include <linux/align.h>
>>>>> #include <net/netdev_queues.h>
>>>>> +#include <linux/pci-tph.h>
>>>>>
>>>>> #include "bnxt_hsi.h"
>>>>> #include "bnxt.h"
>>>>> @@ -10491,6 +10492,7 @@ static void bnxt_free_irq(struct bnxt *bp)
>>>>> free_cpumask_var(irq->cpu_mask);
>>>>> irq->have_cpumask = 0;
>>>>> }
>>>>> + irq_set_affinity_notifier(irq->vector, NULL);
>>>>> free_irq(irq->vector, bp->bnapi[i]);
>>>>> }
>>>>>
>>>>> @@ -10498,6 +10500,45 @@ static void bnxt_free_irq(struct bnxt *bp)
>>>>> }
>>>>> }
>>>>>
>>>>> +static void bnxt_rtnl_lock_sp(struct bnxt *bp);
>>>>> +static void bnxt_rtnl_unlock_sp(struct bnxt *bp);
>>>>> +static void bnxt_irq_affinity_notify(struct irq_affinity_notify *notify,
>>>>> + const cpumask_t *mask)
>>>>> +{
>>>>> + struct bnxt_irq *irq;
>>>>> +
>>>>> + irq = container_of(notify, struct bnxt_irq, affinity_notify);
>>>>> + cpumask_copy(irq->cpu_mask, mask);
>>>>> +
>>>>> + if (!pcie_tph_set_st(irq->bp->pdev, irq->msix_nr,
>>>>> + cpumask_first(irq->cpu_mask),
>>>>> + TPH_MEM_TYPE_VM, PCI_TPH_REQ_TPH_ONLY))
>>>>> + pr_err("error in configuring steering tag\n");
>>>>> +
>>>>> + if (netif_running(irq->bp->dev)) {
>>>>> + rtnl_lock();
>>>>> + bnxt_close_nic(irq->bp, false, false);
>>>>> + bnxt_open_nic(irq->bp, false, false);
>>>>> + rtnl_unlock();
>>>>> + }
>>>>
>>>> Is it really needed? It will cause link flap and pause in the traffic
>>>> service for the device. Why the device needs full restart in this case?
>>>
>>> In that sequence only the rings are recreated for the hardware to sync
>>> up the tags.
>>>
>>> Actually its not a full restart. There is no link reinit or other
>>> heavy lifting in this sequence.
>>> The pause in traffic may be momentary. Do IRQ/CPU affinities change frequently?
>>> Probably not?
>>
>> From what I can see in bnxt_en, proper validation of link_re_init parameter is
>> not (yet?) implemented, __bnxt_open_nic will unconditionally call
>> netif_carrier_off() which will be treated as loss of carrier with counters
>> increment and proper events posted. Changes to CPU affinities were
>> non-disruptive before the patch, but now it may break user-space
>> assumptions.
>
> From my testing the link should not flap. I just fired up a recent net-next
> and confirmed the same by calling $ ethtool -G ens7f0np0 rx 1024 which does a
> similar bnxt_close_nic(bp, false, false)/bnxt_open_nic(bp, false, false) as
> this patch. Link remained up -- even with a non-Broadocm link-partner.
Hi Andy!
Well, it might be that from phy PoV the link didn't flap, but from
network subsystem it does flap:
[root@...t ~]# ethtool -G eth0 rx 512
[root@...t ~]# cat /sys/class/net/eth0/carrier_changes
6
[root@...t ~]# ethtool -G eth0 rx 1024
[root@...t ~]# cat /sys/class/net/eth0/carrier_changes
8
And this is what I'm referring to when talking about user-space
experience. But I would like to see new ndo_queue_stop/start
implementation, it may help in this situation.
>> Does FW need full rings re-init to update target value, which is one u32 write?
>> It looks like overkill TBH.
>
> Full rings do not, but the initialization of that particular ring associated
> with this irq does need to be done. On my list of things we need to do in
> bnxt_en is implement the new ndo_queue_stop/start and ndo_queue_mem_alloc/free
> operations and once those are done we could make a switch as that may be less
> disruptive.
>
>> And yes, affinities can be change on fly according to the changes of the
>> workload on the host.
>>
>>>>
>>>>
>>>>> +}
>>>>> +
>>>>> +static void bnxt_irq_affinity_release(struct kref __always_unused *ref)
>>>>> +{
>>>>> +}
>>>>> +
>>>>> +static inline void __bnxt_register_notify_irqchanges(struct bnxt_irq *irq)
>>>>
>>>> No inlines in .c files, please. Let compiler decide what to inline.
>>>>
>>>>> +{
>>>>> + struct irq_affinity_notify *notify;
>>>>> +
>>>>> + notify = &irq->affinity_notify;
>>>>> + notify->irq = irq->vector;
>>>>> + notify->notify = bnxt_irq_affinity_notify;
>>>>> + notify->release = bnxt_irq_affinity_release;
>>>>> +
>>>>> + irq_set_affinity_notifier(irq->vector, notify);
>>>>> +}
>>>>> +
>>>>> static int bnxt_request_irq(struct bnxt *bp)
>>>>> {
>>>>> int i, j, rc = 0;
>>>>> @@ -10543,6 +10584,7 @@ static int bnxt_request_irq(struct bnxt *bp)
>>>>> int numa_node = dev_to_node(&bp->pdev->dev);
>>>>>
>>>>> irq->have_cpumask = 1;
>>>>> + irq->msix_nr = map_idx;
>>>>> cpumask_set_cpu(cpumask_local_spread(i, numa_node),
>>>>> irq->cpu_mask);
>>>>> rc = irq_set_affinity_hint(irq->vector, irq->cpu_mask);
>>>>> @@ -10552,6 +10594,15 @@ static int bnxt_request_irq(struct bnxt *bp)
>>>>> irq->vector);
>>>>> break;
>>>>> }
>>>>> +
>>>>> + if (!pcie_tph_set_st(bp->pdev, i,
>>>>> + cpumask_first(irq->cpu_mask),
>>>>> + TPH_MEM_TYPE_VM, PCI_TPH_REQ_TPH_ONLY)) {
>>>>> + netdev_err(bp->dev, "error in setting steering tag\n");
>>>>> + } else {
>>>>> + irq->bp = bp;
>>>>> + __bnxt_register_notify_irqchanges(irq);
>>>>> + }
>>>>> }
>>>>> }
>>>>> return rc;
>>>>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
>>>>> index dd849e715c9b..0d3442590bb4 100644
>>>>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
>>>>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
>>>>> @@ -1195,6 +1195,10 @@ struct bnxt_irq {
>>>>> u8 have_cpumask:1;
>>>>> char name[IFNAMSIZ + 2];
>>>>> cpumask_var_t cpu_mask;
>>>>> +
>>>>> + int msix_nr;
>>>>> + struct bnxt *bp;
>>>>> + struct irq_affinity_notify affinity_notify;
>>>>> };
>>>>>
>>>>> #define HWRM_RING_ALLOC_TX 0x1
>>>>
>>
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