Re: [RFCv2 PATCH 14/36] iommu/arm-smmu-v3: Add support for Substream IDs

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On 2017/11/3 17:37, Jean-Philippe Brucker wrote:
> On 03/11/17 05:45, Yisheng Xie wrote:
>> Hi Jean,
>>
>> On 2017/11/3 1:02, Shameerali Kolothum Thodi wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Jean-Philippe Brucker [mailto:Jean-Philippe.Brucker@xxxxxxx]
>>>> Sent: Thursday, November 02, 2017 3:52 PM
>>>> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>
>>>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; linux-
>>>> acpi@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; iommu@lists.linux-
>>>> foundation.org; Mark Rutland <Mark.Rutland@xxxxxxx>; xieyisheng (A)
>>>> <xieyisheng1@xxxxxxxxxx>; Gabriele Paoloni
>>>> <gabriele.paoloni@xxxxxxxxxx>; Catalin Marinas
>>>> <Catalin.Marinas@xxxxxxx>; Will Deacon <Will.Deacon@xxxxxxx>;
>>>> okaya@xxxxxxxxxxxxxx; yi.l.liu@xxxxxxxxx; Lorenzo Pieralisi
>>>> <Lorenzo.Pieralisi@xxxxxxx>; ashok.raj@xxxxxxxxx; tn@xxxxxxxxxxxx;
>>>> joro@xxxxxxxxxx; rfranz@xxxxxxxxxx; lenb@xxxxxxxxxx;
>>>> jacob.jun.pan@xxxxxxxxxxxxxxx; alex.williamson@xxxxxxxxxx;
>>>> robh+dt@xxxxxxxxxx; Leizhen (ThunderTown) <thunder.leizhen@xxxxxxxxxx>;
>>>> bhelgaas@xxxxxxxxxx; dwmw2@xxxxxxxxxxxxx; liubo (CU)
>>>> <liubo95@xxxxxxxxxx>; rjw@xxxxxxxxxxxxx; robdclark@xxxxxxxxx;
>>>> hanjun.guo@xxxxxxxxxx; Sudeep Holla <Sudeep.Holla@xxxxxxx>; Robin
>>>> Murphy <Robin.Murphy@xxxxxxx>; nwatters@xxxxxxxxxxxxxx; Linuxarm
>>>> <linuxarm@xxxxxxxxxx>
>>>> Subject: Re: [RFCv2 PATCH 14/36] iommu/arm-smmu-v3: Add support for
>>>> Substream IDs
>>>>
>>>> Hi Shameer,
>>>>
>>>> On Thu, Nov 02, 2017 at 12:49:32PM +0000, Shameerali Kolothum Thodi wrote:
>>>>> We had a go with this series on HiSIlicon D05 platform which doesn't have
>>>>> support for ssids/ATS/PRI, to make sure it generally works.
>>>>>
>>>>> But observed the below crash on boot,
>>>>>
>>>>> [   16.009084] WARNING: CPU: 59 PID: 391 at mm/page_alloc.c:3883
>>>> __alloc_pages_nodemask+0x19c/0xc48
>>>>> [   16.026797] Modules linked in:
>>>>> [   16.032944] CPU: 59 PID: 391 Comm: kworker/59:1 Not tainted 4.14.0-rc1-
>>>> 159539-ge42aca3 #236
>>>>> [...]
>>>>> [   16.068206] Workqueue: events deferred_probe_work_func
>>>>> [   16.078557] task: ffff8017d38a0000 task.stack: ffff00000b198000
>>>>> [   16.090486] PC is at __alloc_pages_nodemask+0x19c/0xc48
>>>>> [   16.101013] LR is at __alloc_pages_nodemask+0xe0/0xc48
>>>>> [   16.469220] [<ffff000008186b94>] __alloc_pages_nodemask+0x19c/0xc48
>>>>> [   16.481854] [<ffff0000081d65b0>] alloc_pages_current+0x80/0xcc
>>>>> [   16.493607] [<ffff000008182be8>] __get_free_pages+0xc/0x38
>>>>> [   16.504661] [<ffff0000083c4d58>] swiotlb_alloc_coherent+0x64/0x190
>>>>> [   16.517117] [<ffff00000809824c>] __dma_alloc+0x110/0x204
>>>>> [   16.527820] [<ffff00000858e850>] dmam_alloc_coherent+0x88/0xf0
>>>>> [   16.539575] [<ffff000008568884>]
>>>> arm_smmu_domain_finalise_s1+0x60/0x248
>>>>> [   16.552909] [<ffff00000856c104>] arm_smmu_attach_dev+0x264/0x300
>>>>> [   16.565013] [<ffff00000855d40c>] __iommu_attach_device+0x48/0x5c
>>>>> [   16.577117] [<ffff00000855e698>] iommu_group_add_device+0x144/0x3a4
>>>>> [   16.589746] [<ffff00000855ed18>] iommu_group_get_for_dev+0x70/0xf8
>>>>> [   16.602201] [<ffff00000856a314>] arm_smmu_add_device+0x1a4/0x418
>>>>> [   16.614308] [<ffff00000849dfcc>] iort_iommu_configure+0xf0/0x16c
>>>>> [   16.626416] [<ffff000008468c50>] acpi_dma_configure+0x30/0x70
>>>>> [   16.637994] [<ffff00000858f00c>] dma_configure+0xa8/0xd4
>>>>> [   16.648695] [<ffff00000857706c>] driver_probe_device+0x1a4/0x2dc
>>>>> [   16.673081] [<ffff0000085752c8>] bus_for_each_drv+0x54/0x94
>>>>> [   16.684307] [<ffff000008576db0>] __device_attach+0xc4/0x12c
>>>>> [   16.695533] [<ffff000008577350>] device_initial_probe+0x10/0x18
>>>>> [   16.707462] [<ffff0000085762b4>] bus_probe_device+0x90/0x98
>>>>>
>>>>> After a bit of debug it looks like on platforms where ssid is not supported,
>>>>> s1_cfg.num_contexts is set to zero and it eventually results in this crash
>>>>> in,
>>>>> arm_smmu_domain_finalise_s1() -->arm_smmu_alloc_cd_tables()-->
>>>>> arm_smmu_alloc_cd_leaf_table() as num_leaf_entries is zero.
>>>>>
>>>>> With the below fix, it works on D05 now,
>>>>>
>>>>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
>>>>> index 8ad90e2..51f5821 100644
>>>>> --- a/drivers/iommu/arm-smmu-v3.c
>>>>> +++ b/drivers/iommu/arm-smmu-v3.c
>>>>> @@ -2433,7 +2433,10 @@ static int arm_smmu_domain_finalise(struct
>>>> iommu_domain *domain,
>>>>>                         domain->min_pasid = 1;
>>>>>                         domain->max_pasid = master->num_ssids - 1;
>>>>>                         smmu_domain->s1_cfg.num_contexts = master->num_ssids;
>>>>> +               } else {
>>>>> +                       smmu_domain->s1_cfg.num_contexts = 1;
>>>>>                 }
>>>>> +
>>>>>                 smmu_domain->s1_cfg.can_stall = master->ste.can_stall;
>>>>>                 break;
>>>>>         case ARM_SMMU_DOMAIN_NESTED:
>>>>>
>>>>>
>>>>> I am not sure this is right place do this. Please take a look.
>>>>
>>>> Thanks for testing the series and reporting the bug. I added the
>>>> following patch to branch svm/current, does it work for you?
>>>
>>> Yes, it does.
>>>
>>> Thanks,
>>> Shameer
>>>  
>>>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
>>>> index 42c8378624ed..edda466adc81 100644
>>>> --- a/drivers/iommu/arm-smmu-v3.c
>>>> +++ b/drivers/iommu/arm-smmu-v3.c
>>>> @@ -3169,9 +3169,7 @@ static int arm_smmu_add_device(struct device *dev)
>>>>                 }
>>>>         }
>>>>
>>>> -       if (smmu->ssid_bits)
>>>> -               master->num_ssids = 1 << min(smmu->ssid_bits,
>>>> -                                            fwspec->num_pasid_bits);
>>>> +       master->num_ssids = 1 << min(smmu->ssid_bits, fwspec-
>>>>> num_pasid_bits);
>>
>> If fwspec->num_pasid_bits = 0, then master have _one_ num_ssids ?
> 
> Yes, the context table allocator always needs to allocate at least one
> entry, even if the master or SMMU doesn't support SSID. I think an earlier
> version called this field "num_contexts", maybe we should got back to that
> name for clarity?
> 
Yes, it will be more clear.

Thanks
Yisheng

> Thanks,
> Jean
> 
> .
> 

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