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SubjectRe: [PATCH v7 01/11] iommu: Add DMA ownership management interfaces
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Hi Lu,

On 3/7/22 4:27 AM, Lu Baolu wrote:
> Hi Robin,
>
> On 3/4/22 10:10 PM, Robin Murphy wrote:
>> On 2022-03-04 13:55, Eric Auger wrote:
>>> Hi Robin,
>>>
>>> On 3/4/22 1:22 PM, Robin Murphy wrote:
>>>> On 2022-03-04 10:43, Lu Baolu wrote:
>>>>> Hi Eric,
>>>>>
>>>>> On 2022/3/4 18:34, Eric Auger wrote:
>>>>>> I hit a WARN_ON() when unbinding an e1000e driver just after boot:
>>>>>>
>>>>>> sudo modprobe -v vfio-pci
>>>>>> echo vfio-pci | sudo tee -a
>>>>>> /sys/bus/pci/devices/0004:01:00.0/driver_override
>>>>>> vfio-pci
>>>>>> echo 0004:01:00.0 | sudo tee -a  /sys/bus/pci/drivers/e1000e/unbind
>>>>>>
>>>>>>
>>>>>> [  390.042811] ------------[ cut here ]------------
>>>>>> [  390.046468] WARNING: CPU: 42 PID: 5589 at
>>>>>> drivers/iommu/iommu.c:3123
>>>>>> iommu_device_unuse_default_domain+0x68/0x100
>>>>>> [  390.056710] Modules linked in: vfio_pci vfio_pci_core vfio_virqfd
>>>>>> vfio_iommu_type1 vfio xt_CHECKSUM xt_MASQUERADE xt_conntrack
>>>>>> ipt_REJECT
>>>>>> nf_reject_ipv4 nft_compat nft_chain_nat nf_nat nf_conntrack
>>>>>> nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink bridge stp llc
>>>>>> rfkill
>>>>>> sunrpc vfat fat mlx5_ib ib_uverbs ib_core acpi_ipmi ipmi_ssif
>>>>>> ipmi_devintf ipmi_msghandler cppc_cpufreq drm xfs libcrc32c
>>>>>> mlx5_core sg
>>>>>> mlxfw crct10dif_ce tls ghash_ce sha2_ce sha256_arm64 sha1_ce
>>>>>> sbsa_gwdt
>>>>>> e1000e psample sdhci_acpi ahci_platform sdhci libahci_platform
>>>>>> qcom_emac
>>>>>> mmc_core hdma hdma_mgmt dm_mirror dm_region_hash dm_log dm_mod fuse
>>>>>> [  390.110618] CPU: 42 PID: 5589 Comm: tee Kdump: loaded Not tainted
>>>>>> 5.17.0-rc4-lu-v7-official+ #24
>>>>>> [  390.119384] Hardware name: WIWYNN QDF2400 Reference Evaluation
>>>>>> Platform CV90-LA115-P120/QDF2400 Customer Reference Board, BIOS
>>>>>> 0ACJA570
>>>>>> 11/05/2018
>>>>>> [  390.132492] pstate: a0400005 (NzCv daif +PAN -UAO -TCO -DIT -SSBS
>>>>>> BTYPE=--)
>>>>>> [  390.139436] pc : iommu_device_unuse_default_domain+0x68/0x100
>>>>>> [  390.145165] lr : iommu_device_unuse_default_domain+0x38/0x100
>>>>>> [  390.150894] sp : ffff80000fbb3bc0
>>>>>> [  390.154193] x29: ffff80000fbb3bc0 x28: ffff03c0cf6b2400 x27:
>>>>>> 0000000000000000
>>>>>> [  390.161311] x26: 0000000000000000 x25: 0000000000000000 x24:
>>>>>> ffff03c0c7cc5720
>>>>>> [  390.168429] x23: ffff03c0c2b9d150 x22: ffffb4e61df223f8 x21:
>>>>>> ffffb4e61df223f8
>>>>>> [  390.175547] x20: ffff03c7c03c3758 x19: ffff03c7c03c3700 x18:
>>>>>> 0000000000000000
>>>>>> [  390.182665] x17: 0000000000000000 x16: 0000000000000000 x15:
>>>>>> 0000000000000000
>>>>>> [  390.189783] x14: 0000000000000000 x13: 0000000000000030 x12:
>>>>>> ffff03c0d519cd80
>>>>>> [  390.196901] x11: 7f7f7f7f7f7f7f7f x10: 0000000000000dc0 x9 :
>>>>>> ffffb4e620b54f8c
>>>>>> [  390.204019] x8 : ffff03c0cf6b3220 x7 : ffff4ef132bba000 x6 :
>>>>>> 00000000000000ff
>>>>>> [  390.211137] x5 : ffff03c0c2b9f108 x4 : ffff03c0d51f6438 x3 :
>>>>>> 0000000000000000
>>>>>> [  390.218255] x2 : ffff03c0cf6b2400 x1 : 0000000000000000 x0 :
>>>>>> 0000000000000000
>>>>>> [  390.225374] Call trace:
>>>>>> [  390.227804]  iommu_device_unuse_default_domain+0x68/0x100
>>>>>> [  390.233187]  pci_dma_cleanup+0x38/0x44
>>>>>> [  390.236919]  __device_release_driver+0x1a8/0x260
>>>>>> [  390.241519]  device_driver_detach+0x50/0xd0
>>>>>> [  390.245686]  unbind_store+0xf8/0x120
>>>>>> [  390.249245]  drv_attr_store+0x30/0x44
>>>>>> [  390.252891]  sysfs_kf_write+0x50/0x60
>>>>>> [  390.256537]  kernfs_fop_write_iter+0x134/0x1cc
>>>>>> [  390.260964]  new_sync_write+0xf0/0x18c
>>>>>> [  390.264696]  vfs_write+0x230/0x2d0
>>>>>> [  390.268082]  ksys_write+0x74/0x100
>>>>>> [  390.271467]  __arm64_sys_write+0x28/0x3c
>>>>>> [  390.275373]  invoke_syscall.constprop.0+0x58/0xf0
>>>>>> [  390.280061]  el0_svc_common.constprop.0+0x160/0x164
>>>>>> [  390.284922]  do_el0_svc+0x34/0xcc
>>>>>> [  390.288221]  el0_svc+0x30/0x140
>>>>>> [  390.291346]  el0t_64_sync_handler+0xa4/0x130
>>>>>> [  390.295599]  el0t_64_sync+0x1a0/0x1a4
>>>>>> [  390.299245] ---[ end trace 0000000000000000 ]---
>>>>>>
>>>>>>
>>>>>> I put some traces in the code and I can see that
>>>>>> iommu_device_use_default_domain() effectively is called on
>>>>>> 0004:01:00.0 e1000e device on pci_dma_configure() but at that time
>>>>>> the iommu group is NULL:
>>>>>> [   10.569427] e1000e 0004:01:00.0: ------ ENTRY pci_dma_configure
>>>>>> driver_managed_area=0
>>>>>> [   10.569431] e1000e 0004:01:00.0: ****
>>>>>> iommu_device_use_default_domain ENTRY
>>>>>> [   10.569433] e1000e 0004:01:00.0: ****
>>>>>> iommu_device_use_default_domain no group
>>>>>> [   10.569435] e1000e 0004:01:00.0: pci_dma_configure
>>>>>> iommu_device_use_default_domain returned 0
>>>>>> [   10.569492] e1000e 0004:01:00.0: Adding to iommu group 3
>>>>>>
>>>>>> ^^^the group is added after the
>>>>>> iommu_device_use_default_domain() call
>>>>>> So the group->owner_cnt is not incremented as expected.
>>>>>
>>>>> Thank you for reporting this. Do you have any idea why the driver is
>>>>> loaded before iommu_probe_device()?
>>>>
>>>> Urgh, this is the horrible firmware-data-ordering thing again. The
>>>> stuff I've been saying about having to rework the whole .dma_configure
>>>> mechanism in the near future is to fix this properly.
>>>>
>>>> The summary is that in patch #4, calling
>>>> iommu_device_use_default_domain() *before* {of,acpi}_dma_configure is
>>>> currently a problem. As things stand, the IOMMU driver ignored the
>>>> initial iommu_probe_device() call when the device was added, since at
>>>> that point it had no fwspec yet. In this situation,
>>>> {of,acpi}_iommu_configure() are retriggering iommu_probe_device()
>>>> after the IOMMU driver has seen the firmware data via .of_xlate to
>>>> learn that it it actually responsible for the given device.
>>>
>>> thank you for providing the info. Hope this is something Lu can work
>>> around.
>>
>> Hopefully it's just a case of flipping the calls around, so that
>> iommu_use_default_domain() goes at the end, and calls
>> arch_teardown_dma_ops() if it fails. From a quick skim I *think* that
>> should still work out to the desired behaviour (or at least close
>> enough that we can move forward without a circular dependency between
>> fixes...)
>
> This is a reasonable solution to me. Thank you for the information and
> suggestion.
>
> Eric, I have updated the patch #4 and uploaded a new version here:
>
> https://github.com/LuBaolu/intel-iommu/commits/iommu-dma-ownership-v8

with v8 I do not hit the warning anymore and the owner accounting seems
to work as expected.

Thanks

Eric
>
> Can you please give it a try?
>
> Best regards,
> baolu
>

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