Re: warning from domain_get_iommu

[Jerry Snitselaar <jsnitsel@redhat.com>]

On Sat Feb 08 20, Lu Baolu wrote:
>Hi Jerry,
>
>On 2020/2/7 17:34, Jerry Snitselaar wrote:
>>On Thu Feb 06 20, Jerry Snitselaar wrote:
>>>On Tue Feb 04 20, Jerry Snitselaar wrote:
>>>>I'm working on getting a system to reproduce this, and verify it 
>>>>also occurs
>>>>with 5.5, but I have a report of a case where the kdump kernel gives
>>>>warnings like the following on a hp dl360 gen9:
>>>>
>>>>[    2.830589] ehci_hcd: USB 2.0 'Enhanced' Host Controller 
>>>>(EHCI) Driver
>>>>[    2.832615] ehci-pci: EHCI PCI platform driver
>>>>[    2.834190] ehci-pci 0000:00:1a.0: EHCI Host Controller
>>>>[    2.835974] ehci-pci 0000:00:1a.0: new USB bus registered, 
>>>>assigned bus number 1
>>>>[    2.838276] ehci-pci 0000:00:1a.0: debug port 2
>>>>[    2.839700] WARNING: CPU: 0 PID: 1 at 
>>>>drivers/iommu/intel-iommu.c:598 domain_get_iommu+0x55/0x60
>>>>[    2.840671] Modules linked in:
>>>>[    2.840671] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 
>>>>4.18.0-170.el8.kdump2.x86_64 #1
>>>>[    2.840671] Hardware name: HP ProLiant DL360 Gen9/ProLiant 
>>>>DL360 Gen9, BIOS P89 07/21/2019
>>>>[    2.840671] RIP: 0010:domain_get_iommu+0x55/0x60
>>>>[    2.840671] Code: c2 01 eb 0b 48 83 c0 01 8b 34 87 85 f6 75 
>>>>0b 48 63 c8 48 39 c2 75 ed 31 c0 c3 48 c1 e1 03 48 8b 05 70 f3 
>>>>91 01 48 8b 04 08 c3 <0f> 0b 31 c0 c3 31 c9 eb eb 66 90 0f 1f 44 
>>>>00 00 41 55 40 0f b6 f6
>>>>[    2.840671] RSP: 0018:ffffc900000dfab8 EFLAGS: 00010202
>>>>[    2.840671] RAX: ffff88ec7f1c8000 RBX: 0000006c7c867000 RCX: 
>>>>0000000000000000
>>>>[    2.840671] RDX: 00000000fffffff0 RSI: 0000000000000000 RDI: 
>>>>ffff88ec7f1c8000
>>>>[    2.840671] RBP: ffff88ec6f7000b0 R08: ffff88ec7f19d000 R09: 
>>>>ffff88ec7cbfcd00
>>>>[    2.840671] R10: 0000000000000095 R11: ffffc900000df928 R12: 
>>>>0000000000000000
>>>>[    2.840671] R13: ffff88ec7f1c8000 R14: 0000000000001000 R15: 
>>>>00000000ffffffff
>>>>[    2.840671] FS:  0000000000000000(0000) 
>>>>GS:ffff88ec7f600000(0000) knlGS:0000000000000000
>>>>[    2.840671] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>[    2.840671] CR2: 00007ff3e1713000 CR3: 0000006c7de0a004 CR4: 
>>>>00000000001606b0
>>>>[    2.840671] Call Trace:
>>>>[    2.840671]  __intel_map_single+0x62/0x140
>>>>[    2.840671]  intel_alloc_coherent+0xa6/0x130
>>>>[    2.840671]  dma_pool_alloc+0xd8/0x1e0
>>>>[    2.840671]  e_qh_alloc+0x55/0x130
>>>>[    2.840671]  ehci_setup+0x284/0x7b0
>>>>[    2.840671]  ehci_pci_setup+0xa3/0x530
>>>>[    2.840671]  usb_add_hcd+0x2b6/0x800
>>>>[    2.840671]  usb_hcd_pci_probe+0x375/0x460
>>>>[    2.840671]  local_pci_probe+0x41/0x90
>>>>[    2.840671]  pci_device_probe+0x105/0x1b0
>>>>[    2.840671]  driver_probe_device+0x12d/0x460
>>>>[    2.840671]  device_driver_attach+0x50/0x60
>>>>[    2.840671]  __driver_attach+0x61/0x130
>>>>[    2.840671]  ? device_driver_attach+0x60/0x60
>>>>[    2.840671]  bus_for_each_dev+0x77/0xc0
>>>>[    2.840671]  ? klist_add_tail+0x3b/0x70
>>>>[    2.840671]  bus_add_driver+0x14d/0x1e0
>>>>[    2.840671]  ? ehci_hcd_init+0xaa/0xaa
>>>>[    2.840671]  ? do_early_param+0x91/0x91
>>>>[    2.840671]  driver_register+0x6b/0xb0
>>>>[    2.840671]  ? ehci_hcd_init+0xaa/0xaa
>>>>[    2.840671]  do_one_initcall+0x46/0x1c3
>>>>[    2.840671]  ? do_early_param+0x91/0x91
>>>>[    2.840671]  kernel_init_freeable+0x1af/0x258
>>>>[    2.840671]  ? rest_init+0xaa/0xaa
>>>>[    2.840671]  kernel_init+0xa/0xf9
>>>>[    2.840671]  ret_from_fork+0x35/0x40
>>>>[    2.840671] ---[ end trace e87b0d9a1c8135c4 ]---
>>>>[    3.010848] ehci-pci 0000:00:1a.0: Using iommu dma mapping
>>>>[    3.012551] ehci-pci 0000:00:1a.0: 32bit DMA uses 
>>>>non-identity mapping
>>>>[    3.018537] ehci-pci 0000:00:1a.0: cache line size of 64 is 
>>>>not supported
>>>>[    3.021188] ehci-pci 0000:00:1a.0: irq 18, io mem 0x93002000
>>>>[    3.029006] ehci-pci 0000:00:1a.0: USB 2.0 started, EHCI 1.00
>>>>[    3.030918] usb usb1: New USB device found, idVendor=1d6b, 
>>>>idProduct=0002, bcdDevice= 4.18
>>>>[    3.033491] usb usb1: New USB device strings: Mfr=3, 
>>>>Product=2, SerialNumber=1
>>>>[    3.035900] usb usb1: Product: EHCI Host Controller
>>>>[    3.037423] usb usb1: Manufacturer: Linux 
>>>>4.18.0-170.el8.kdump2.x86_64 ehci_hcd
>>>>[    3.039691] usb usb1: SerialNumber: 0000:00:1a.0
>>>>
>>>>It looks like the device finishes initializing once it figures out it
>>>>needs dma mapping instead of the default
>>>>passthrough. intel_alloc_coherent calls iommu_need_mapping, before it
>>>>calls __intel_map_single, so I'm not sure why it is tripping over the
>>>>WARN_ON in domain_get_iommu.
>>>>
>>>>one thing I noticed while looking at this is that domain_get_iommu can
>>>>return NULL. So should there be something like the following in
>>>>__intel_map_single after the domain_get_iommu call?
>>>>
>>>>if (!iommu)
>>>> goto error;
>>>>
>>>>It is possible to deref the null pointer later otherwise.
>>>>
>>>>Regards,
>>>>Jerry
>>>
>>>I reproduced the warning with a 5.5 kernel on an Intel NUC5i5MYBE.
>>
>>Hi Baolu,
>>
>>I think I understand what is happening here. With the kdump boot
>>translation is pre-enabled, so in intel_iommu_add_device things are
>>getting set to DEFER_DEVICE_DOMAIN_INFO. When intel_alloc_coherent
>>calls iommu_need_mapping it returns true, but doesn't do the dma
>>domain switch because of DEFER_DEVICE_DOMAIN_INFO. Then
>>__intel_map_single gets called and it calls deferred_attach_domain,
>>which sets the domain to the group domain, which in this case is the
>>identity domain. Then it calls domain_get_iommu, which spits out the
>>warning because the domain type was dma and returns null. My
>>workaround was to add a call to iommu_need_mapping and find_domain
>>after the deferred_attach_domain, but I don't know if that is the
>>correct solution. There are a couple other spots like intel_map_sg
>>that have the deferred_attach_domain after iommu_need_mapping that
>>possibly will suffer from the same problem.
>>
>>diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>>index b5c5ab58d395..063f45323cfc 100644
>>--- a/drivers/iommu/intel-iommu.c
>>+++ b/drivers/iommu/intel-iommu.c
>>@@ -3515,6 +3515,10 @@ static dma_addr_t __intel_map_single(struct 
>>device *dev, phys_addr_t paddr,
>>         if (!domain)
>>                 return DMA_MAPPING_ERROR;
>>
>>+       if (!iommu_need_mapping(dev))
>>+               return paddr;
>>+
>>+       domain = find_domain(dev);
>>         iommu = domain_get_iommu(domain);
>>         size = aligned_nrpages(paddr, size);
>>
>>
>>I finally got a git repo over to one of these systems, and was
>>able to reproduce the issue with the head of linus's tree. With commit
>>9235cb13d7d1 ("iommu/vt-d: Allow devices with RMRRs to use identity 
>>domain")
>>there are more of the warnings, because devices are using identity that
>>weren't before.
>>
>
>Is it possible to move deferred domain attachment to identity_mapping()?
>
>diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>index 9dc37672bf89..234ab346198e 100644
>--- a/drivers/iommu/intel-iommu.c
>+++ b/drivers/iommu/intel-iommu.c
>@@ -2913,13 +2913,11 @@ static int __init si_domain_init(int hw)
>
> static int identity_mapping(struct device *dev)
> {
>-       struct device_domain_info *info;
>+       struct dmar_domain *domain;
>
>-       info = dev->archdata.iommu;
>-       if (info && info != DUMMY_DEVICE_DOMAIN_INFO && info != 
>DEFER_DEVICE_DOMAIN_INFO)
>-               return (info->domain == si_domain);
>+       domain = deferred_attach_domain(dev);
>
>-       return 0;
>+       return (!domain || domain_type_is_si(domain));
> }
>
> static int domain_add_dev_info(struct dmar_domain *domain, struct 
>device *dev)
>
>Best regards,
>baolu

Hi Baolu,

I think that would work, and then change the deferred_attach_domain
calls in __intel_map_single and intel_map_sg to find_domain?

I did a quick test with it on the system where I've been looking at this.

Regards,
Jerry

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