iommu/arm-smmu: Don't unregister on shutdown
commit ce31e6ca upstream. Michael Walle says he noticed the following stack trace while performing a shutdown with "reboot -f". He suggests he got "lucky" and just hit the correct spot for the reboot while there was a packet transmission in flight. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000098 CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 6.1.0-rc5-00088-gf3600ff8e322 #1930 Hardware name: Kontron KBox A-230-LS (DT) pc : iommu_get_dma_domain+0x14/0x20 lr : iommu_dma_map_page+0x9c/0x254 Call trace: iommu_get_dma_domain+0x14/0x20 dma_map_page_attrs+0x1ec/0x250 enetc_start_xmit+0x14c/0x10b0 enetc_xmit+0x60/0xdc dev_hard_start_xmit+0xb8/0x210 sch_direct_xmit+0x11c/0x420 __dev_queue_xmit+0x354/0xb20 ip6_finish_output2+0x280/0x5b0 __ip6_finish_output+0x15c/0x270 ip6_output+0x78/0x15c NF_HOOK.constprop.0+0x50/0xd0 mld_sendpack+0x1bc/0x320 mld_ifc_work+0x1d8/0x4dc process_one_work+0x1e8/0x460 worker_thread+0x178/0x534 kthread+0xe0/0xe4 ret_from_fork+0x10/0x20 Code: d503201f f9416800 d503233f d50323bf (f9404c00) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception in interrupt This appears to be reproducible when the board has a fixed IP address, is ping flooded from another host, and "reboot -f" is used. The following is one more manifestation of the issue: $ reboot -f kvm: exiting hardware virtualization cfg80211: failed to load regulatory.db arm-smmu 5000000.iommu: disabling translation sdhci-esdhc 2140000.mmc: Removing from iommu group 11 sdhci-esdhc 2150000.mmc: Removing from iommu group 12 fsl-edma 22c0000.dma-controller: Removing from iommu group 17 dwc3 3100000.usb: Removing from iommu group 9 dwc3 3110000.usb: Removing from iommu group 10 ahci-qoriq 3200000.sata: Removing from iommu group 2 fsl-qdma 8380000.dma-controller: Removing from iommu group 20 platform f080000.display: Removing from iommu group 0 etnaviv-gpu f0c0000.gpu: Removing from iommu group 1 etnaviv etnaviv: Removing from iommu group 1 caam_jr 8010000.jr: Removing from iommu group 13 caam_jr 8020000.jr: Removing from iommu group 14 caam_jr 8030000.jr: Removing from iommu group 15 caam_jr 8040000.jr: Removing from iommu group 16 fsl_enetc 0000:00:00.0: Removing from iommu group 4 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000002, GFSYNR1 0x00000429, GFSYNR2 0x00000000 fsl_enetc 0000:00:00.1: Removing from iommu group 5 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000002, GFSYNR1 0x00000429, GFSYNR2 0x00000000 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000000, GFSYNR1 0x00000429, GFSYNR2 0x00000000 fsl_enetc 0000:00:00.2: Removing from iommu group 6 fsl_enetc_mdio 0000:00:00.3: Removing from iommu group 8 mscc_felix 0000:00:00.5: Removing from iommu group 3 fsl_enetc 0000:00:00.6: Removing from iommu group 7 pcieport 0001:00:00.0: Removing from iommu group 18 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x00000002, GFSYNR0 0x00000000, GFSYNR1 0x00000429, GFSYNR2 0x00000000 pcieport 0002:00:00.0: Removing from iommu group 19 Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a8 pc : iommu_get_dma_domain+0x14/0x20 lr : iommu_dma_unmap_page+0x38/0xe0 Call trace: iommu_get_dma_domain+0x14/0x20 dma_unmap_page_attrs+0x38/0x1d0 enetc_unmap_tx_buff.isra.0+0x6c/0x80 enetc_poll+0x170/0x910 __napi_poll+0x40/0x1e0 net_rx_action+0x164/0x37c __do_softirq+0x128/0x368 run_ksoftirqd+0x68/0x90 smpboot_thread_fn+0x14c/0x190 Code: d503201f f9416800 d503233f d50323bf (f9405400) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception in interrupt ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]--- The problem seems to be that iommu_group_remove_device() is allowed to run with no coordination whatsoever with the shutdown procedure of the enetc PCI device. In fact, it almost seems as if it implies that the pci_driver :: shutdown() method is mandatory if DMA is used with an IOMMU, otherwise this is inevitable. That was never the case; shutdown methods are optional in device drivers. This is the call stack that leads to iommu_group_remove_device() during reboot: kernel_restart -> device_shutdown -> platform_shutdown -> arm_smmu_device_shutdown -> arm_smmu_device_remove -> iommu_device_unregister -> bus_for_each_dev -> remove_iommu_group -> iommu_release_device -> iommu_group_remove_device I don't know much about the arm_smmu driver, but arm_smmu_device_shutdown() invoking arm_smmu_device_remove() looks suspicious, since it causes the IOMMU device to unregister and that's where everything starts to unravel. It forces all other devices which depend on IOMMU groups to also point their ->shutdown() to ->remove(), which will make reboot slower overall. There are 2 moments relevant to this behavior. First was commit b06c076e ("Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular"") when arm_smmu_device_shutdown() was made to run the exact same thing as arm_smmu_device_remove(). Prior to that, there was no iommu_device_unregister() call in arm_smmu_device_shutdown(). However, that was benign until commit 57365a04 ("iommu: Move bus setup to IOMMU device registration"), which made iommu_device_unregister() call remove_iommu_group(). Restore the old shutdown behavior by making remove() call shutdown(), but shutdown() does not call the remove() specific bits. Fixes: 57365a04 ("iommu: Move bus setup to IOMMU device registration") Reported-by:Michael Walle <michael@walle.cc> Tested-by: Michael Walle <michael@walle.cc> # on kontron-sl28 Signed-off-by:
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