Messages in this thread Patch in this message | | | Date | Fri, 7 Feb 2020 02:34:13 -0700 | From | Jerry Snitselaar <> | Subject | Re: warning from domain_get_iommu |
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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.
Regards, Jerry
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