Hi Jean,

-----Original Message-----
From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@lists.infradead.org]
On Behalf Of Jean-Philippe Brucker
Sent: Friday, October 06, 2017 2:32 PM
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acpi@vger.kernel.org; devicetree@vger.kernel.org; iommu@lists.linux-
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Subject: [RFCv2 PATCH 14/36] iommu/arm-smmu-v3: Add support for
Substream IDs

At the moment, the SMMUv3 driver offers only one stage-1 or stage-2
address space to each device. SMMUv3 allows to associate multiple address
spaces per device. In addition to the Stream ID (SID), that identifies a
device, we can now have Substream IDs (SSID) identifying an address space.
In PCIe lingo, SID is called Requester ID (RID) and SSID is called Process
Address-Space ID (PASID).

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,
Shameer