Message-ID: <86B0E564-52C0-457E-A101-1BC4D6E22AC2@oracle.com>
Date: Tue, 30 May 2023 13:51:02 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Eli Cohen <elic@...dia.com>
CC: Shay Drory <shayd@...dia.com>, Leon Romanovsky <leon@...nel.org>,
        Saeed
 Mahameed <saeedm@...dia.com>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        "open
 list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        Thomas Gleixner
	<tglx@...utronix.de>
Subject: Re: system hang on start-up (mlx5?)



> On May 30, 2023, at 9:48 AM, Eli Cohen <elic@...dia.com> wrote:
> 
>> From: Chuck Lever III <chuck.lever@...cle.com>
>> Sent: Tuesday, 30 May 2023 16:28
>> To: Eli Cohen <elic@...dia.com>
>> Cc: Leon Romanovsky <leon@...nel.org>; Saeed Mahameed
>> <saeedm@...dia.com>; linux-rdma <linux-rdma@...r.kernel.org>; open
>> list:NETWORKING [GENERAL] <netdev@...r.kernel.org>; Thomas Gleixner
>> <tglx@...utronix.de>
>> Subject: Re: system hang on start-up (mlx5?)
>> 
>> 
>> 
>>> On May 30, 2023, at 9:09 AM, Chuck Lever III <chuck.lever@...cle.com>
>> wrote:
>>> 
>>>> On May 29, 2023, at 5:20 PM, Thomas Gleixner <tglx@...utronix.de>
>> wrote:
>>>> 
>>>> On Sat, May 27 2023 at 20:16, Chuck Lever, III wrote:
>>>>>> On May 7, 2023, at 1:31 AM, Eli Cohen <elic@...dia.com> wrote:
>>>>> I can boot the system with mlx5_core deny-listed. I log in, remove
>>>>> mlx5_core from the deny list, and then "modprobe mlx5_core" to
>>>>> reproduce the issue while the system is running.
>>>>> 
>>>>> May 27 15:47:45 manet.1015granger.net kernel: mlx5_core 0000:81:00.0:
>> firmware version: 16.35.2000
>>>>> May 27 15:47:45 manet.1015granger.net kernel: mlx5_core 0000:81:00.0:
>> 126.016 Gb/s available PCIe bandwidth (8.0 GT/s PCIe x16 link)
>>>>> May 27 15:47:46 manet.1015granger.net kernel: mlx5_irq_alloc:
>> pool=ffff9a3718e56180 i=0 af_desc=ffffb6c88493fc90
>>>>> May 27 15:47:46 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a3aefcf0f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:46 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a3aefcf0f60 end=236
>>>>> May 27 15:47:46 manet.1015granger.net kernel: mlx5_core 0000:81:00.0:
>> Port module event: module 0, Cable plugged
>>>>> May 27 15:47:46 manet.1015granger.net kernel: mlx5_irq_alloc:
>> pool=ffff9a3718e56180 i=1 af_desc=ffffb6c88493fc60
>>>>> May 27 15:47:46 manet.1015granger.net kernel: mlx5_core 0000:81:00.0:
>> mlx5_pcie_event:301:(pid 10): PCIe slot advertised sufficient power (27W).
>>>>> May 27 15:47:46 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a36efcf0f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a36efcf0f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a36efd30f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a36efd30f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a3aefc30f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a3aefc30f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a3aefc70f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a3aefc70f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a3aefd30f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a3aefd30f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffff9a3aefd70f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->alloc_map=ffff9a3aefd70f60 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: matrix_alloc_area: m-
>>> scratch_map=ffff9a33801990b0 cm->managed_map=ffffffffb9ef3f80 m-
>>> system_map=ffff9a33801990d0 end=236
>>>>> May 27 15:47:47 manet.1015granger.net kernel: BUG: unable to handle
>> page fault for address: ffffffffb9ef3f80
>>>>> 
>>>>> ###
>>>>> 
>>>>> The fault address is the cm->managed_map for one of the CPUs.
>>>> 
>>>> That does not make any sense at all. The irq matrix is initialized via:
>>>> 
>>>> irq_alloc_matrix()
>>>> m = kzalloc(sizeof(matric);
>>>> m->maps = alloc_percpu(*m->maps);
>>>> 
>>>> So how is any per CPU map which got allocated there supposed to be
>>>> invalid (not mapped):
>>>> 
>>>>> May 27 15:47:47 manet.1015granger.net kernel: BUG: unable to handle
>> page fault for address: ffffffffb9ef3f80
>>>>> May 27 15:47:47 manet.1015granger.net kernel: #PF: supervisor read
>> access in kernel mode
>>>>> May 27 15:47:47 manet.1015granger.net kernel: #PF: error_code(0x0000)
>> - not-present page
>>>>> May 27 15:47:47 manet.1015granger.net kernel: PGD 54ec19067 P4D
>> 54ec19067 PUD 54ec1a063 PMD 482b83063 PTE 800ffffab110c062
>>>> 
>>>> But if you look at the address: 0xffffffffb9ef3f80
>>>> 
>>>> That one is bogus:
>>>> 
>>>>   managed_map=ffff9a36efcf0f80
>>>>   managed_map=ffff9a36efd30f80
>>>>   managed_map=ffff9a3aefc30f80
>>>>   managed_map=ffff9a3aefc70f80
>>>>   managed_map=ffff9a3aefd30f80
>>>>   managed_map=ffff9a3aefd70f80
>>>>   managed_map=ffffffffb9ef3f80
>>>> 
>>>> Can you spot the fail?
>>>> 
>>>> The first six are in the direct map and the last one is in module map,
>>>> which makes no sense at all.
>>> 
>>> Indeed. The reason for that is that the affinity mask has bits
>>> set for CPU IDs that are not present on my system.
>>> 
>>> After bbac70c74183 ("net/mlx5: Use newer affinity descriptor")
>>> that mask is set up like this:
>>> 
>>> struct mlx5_irq *mlx5_ctrl_irq_request(struct mlx5_core_dev *dev)
>>> {
>>>       struct mlx5_irq_pool *pool = ctrl_irq_pool_get(dev);
>>> -       cpumask_var_t req_mask;
>>> +       struct irq_affinity_desc af_desc;
>>>       struct mlx5_irq *irq;
>>> -       if (!zalloc_cpumask_var(&req_mask, GFP_KERNEL))
>>> -               return ERR_PTR(-ENOMEM);
>>> -       cpumask_copy(req_mask, cpu_online_mask);
>>> +       cpumask_copy(&af_desc.mask, cpu_online_mask);
>>> +       af_desc.is_managed = false;
>> 
>> By the way, why is "is_managed" set to false?
>> 
>> This particular system is a NUMA system, and I'd like to be
>> able to set IRQ affinity for the card. Since is_managed is
>> set to false, writing to the /proc/irq files fails with EIO.
>> 
> This is a control irq and is used for issuing configuration commands.
> 
> This commit:
> commit c410abbbacb9b378365ba17a30df08b4b9eec64f
> Author: Dou Liyang <douliyangs@...il.com>
> Date:   Tue Dec 4 23:51:21 2018 +0800
> 
>    genirq/affinity: Add is_managed to struct irq_affinity_desc
> 
> explains why it should not be managed.

Understood, but what about the other IRQs? I can't set any
of them. All writes to the proc files result in EIO.


>>> Which normally works as you would expect. But for some historical
>>> reason, I have CONFIG_NR_CPUS=32 on my system, and the
>>> cpumask_copy() misbehaves.
>>> 
>>> If I correct mlx5_ctrl_irq_request() to clear @af_desc before the
>>> copy, this crash goes away. But mlx5_core crashes during a later
>>> part of its init, in cpu_rmap_update(). cpu_rmap_update() does
>>> exactly the same thing (for_each_cpu() on an affinity mask created
>>> by copying), and crashes in a very similar fashion.
>>> 
>>> If I set CONFIG_NR_CPUS to a larger value, like 512, the problem
>>> vanishes entirely, and "modprobe mlx5_core" works as expected.
>>> 
>>> Thus I think the problem is with cpumask_copy() or for_each_cpu()
>>> when NR_CPUS is a small value (the default is 8192).
>>> 
>>> 
>>>> Can you please apply the debug patch below and provide the output?
>>>> 
>>>> Thanks,
>>>> 
>>>>      tglx
>>>> ---
>>>> --- a/kernel/irq/matrix.c
>>>> +++ b/kernel/irq/matrix.c
>>>> @@ -51,6 +51,7 @@ struct irq_matrix {
>>>> unsigned int alloc_end)
>>>> {
>>>> struct irq_matrix *m;
>>>> + unsigned int cpu;
>>>> 
>>>> if (matrix_bits > IRQ_MATRIX_BITS)
>>>> return NULL;
>>>> @@ -68,6 +69,8 @@ struct irq_matrix {
>>>> kfree(m);
>>>> return NULL;
>>>> }
>>>> + for_each_possible_cpu(cpu)
>>>> + pr_info("ALLOC: CPU%03u: %016lx\n", cpu, (unsigned
>> long)per_cpu_ptr(m->maps, cpu));
>>>> return m;
>>>> }
>>>> 
>>>> @@ -215,6 +218,8 @@ int irq_matrix_reserve_managed(struct ir
>>>> struct cpumap *cm = per_cpu_ptr(m->maps, cpu);
>>>> unsigned int bit;
>>>> 
>>>> + pr_info("RESERVE MANAGED: CPU%03u: %016lx\n", cpu, (unsigned
>> long)cm);
>>>> +
>>>> bit = matrix_alloc_area(m, cm, 1, true);
>>>> if (bit >= m->alloc_end)
>>>> goto cleanup;
>>> 
>>> --
>>> Chuck Lever
>> 
>> 
>> --
>> Chuck Lever


--
Chuck Lever

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