Message-ID: <FD9A2C0A-1E3A-4D5B-9529-49F140771AAE@oracle.com>
Date: Tue, 30 May 2023 13:28:00 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
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.


> 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

Powered by blists - more mailing lists