Re: Failure to recreate virtual functions

[Robin Murphy <robin.murphy@arm.com>]

On 30/07/2019 05:28, Lu Baolu wrote:
> Hi,
> 
> On 7/29/19 6:05 PM, Vlad Buslov wrote:
>> On Sat 27 Jul 2019 at 05:15, Lu Baolu<baolu.lu@linux.intel.com>  wrote:
>>> Hi Vilad,
>>>
>>> On 7/27/19 12:30 AM, Vlad Buslov wrote:
>>>> Hi Lu Baolu,
>>>>
>>>> Our mlx5 driver fails to recreate VFs when cmdline includes
>>>> "intel_iommu=on iommu=pt" after recent merge of patch set "iommu/vt-d:
>>>> Delegate DMA domain to generic iommu". I've bisected the failure to
>>>> patch b7297783c2bb ("iommu/vt-d: Remove duplicated code for device
>>>> hotplug"). Here is the dmesg log for following case: enable switchdev
>>>> mode, set number of VFs to 0, then set it back to any value
>>>>> 0.
>>>> [  223.525282] mlx5_core 0000:81:00.0: E-Switch: E-Switch enable 
>>>> SRIOV: nvfs(2) mode (1)
>>>> [  223.562027] mlx5_core 0000:81:00.0: E-Switch: SRIOV enabled: 
>>>> active vports(3)
>>>> [  223.663766] pci 0000:81:00.2: [15b3:101a] type 00 class 0x020000
>>>> [  223.663864] pci 0000:81:00.2: enabling Extended Tags
>>>> [  223.665143] pci 0000:81:00.2: Adding to iommu group 52
>>>> [  223.665215] pci 0000:81:00.2: Using iommu direct mapping
>>>> [  223.665771] mlx5_core 0000:81:00.2: enabling device (0000 -> 0002)
>>>> [  223.665890] mlx5_core 0000:81:00.2: firmware version: 16.26.148
>>>> [  223.889908] mlx5_core 0000:81:00.2: Rate limit: 127 rates are 
>>>> supported, range: 0Mbps to 97656Mbps
>>>> [  223.896438] mlx5_core 0000:81:00.2: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  223.896636] mlx5_core 0000:81:00.2: Assigned random MAC address 
>>>> 56:1f:95:e0:51:d6
>>>> [  224.012905] mlx5_core 0000:81:00.2 ens1f0v0: renamed from eth0
>>>> [  224.041651] pci 0000:81:00.3: [15b3:101a] type 00 class 0x020000
>>>> [  224.041711] pci 0000:81:00.3: enabling Extended Tags
>>>> [  224.043660] pci 0000:81:00.3: Adding to iommu group 53
>>>> [  224.043738] pci 0000:81:00.3: Using iommu direct mapping
>>>> [  224.044196] mlx5_core 0000:81:00.3: enabling device (0000 -> 0002)
>>>> [  224.044298] mlx5_core 0000:81:00.3: firmware version: 16.26.148
>>>> [  224.268099] mlx5_core 0000:81:00.3: Rate limit: 127 rates are 
>>>> supported, range: 0Mbps to 97656Mbps
>>>> [  224.274983] mlx5_core 0000:81:00.3: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  224.275195] mlx5_core 0000:81:00.3: Assigned random MAC address 
>>>> a6:1e:56:0a:d9:f2
>>>> [  224.388359] mlx5_core 0000:81:00.3 ens1f0v1: renamed from eth0
>>>> [  236.325027] mlx5_core 0000:81:00.0: E-Switch: disable SRIOV: 
>>>> active vports(3) mode(1)
>>>> [  236.362766] mlx5_core 0000:81:00.0: E-Switch: E-Switch enable 
>>>> SRIOV: nvfs(2) mode (2)
>>>> [  237.290066] mlx5_core 0000:81:00.0: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  237.350215] mlx5_core 0000:81:00.0: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  237.373052] mlx5_core 0000:81:00.0 ens1f0: renamed from eth0
>>>> [  237.390768] mlx5_core 0000:81:00.0: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  237.447846] ens1f0_0: renamed from eth0
>>>> [  237.460399] mlx5_core 0000:81:00.0: E-Switch: SRIOV enabled: 
>>>> active vports(3)
>>>> [  237.526880] ens1f0_1: renamed from eth1
>>>> [  248.953873] pci 0000:81:00.2: Removing from iommu group 52
>>>> [  248.954114] pci 0000:81:00.3: Removing from iommu group 53
>>>> [  249.960570] mlx5_core 0000:81:00.0: E-Switch: disable SRIOV: 
>>>> active vports(3) mode(2)
>>>> [  250.319135] mlx5_core 0000:81:00.0: MLX5E: StrdRq(1) RqSz(8) 
>>>> StrdSz(2048) RxCqeCmprss(0)
>>>> [  250.559431] mlx5_core 0000:81:00.0 ens1f0: renamed from eth0
>>>> [  258.819162] mlx5_core 0000:81:00.0: E-Switch: E-Switch enable 
>>>> SRIOV: nvfs(2) mode (1)
>>>> [  258.831625] mlx5_core 0000:81:00.0: E-Switch: SRIOV enabled: 
>>>> active vports(3)
>>>> [  258.936160] pci 0000:81:00.2: [15b3:101a] type 00 class 0x020000
>>>> [  258.936258] pci 0000:81:00.2: enabling Extended Tags
>>>> [  258.937438] pci 0000:81:00.2: Failed to add to iommu group 52: -16
>>> It seems that an EBUSY error returned from iommu_group_add_device(). Can
>>> you please hack some debug messages in iommu_group_add_device() so that
>>> we can know where the EBUSY returns?
>>>
>>> Best regards,
>>> Baolu
>> The error code is returned by __iommu_attach_device().
>>
> 
> Thanks!
> 
> It looks like the system has already a domain for specific pci bdf
> device. Does this VF share the bdf with other devices? Or has been
> previously created, and system failed to get chance to remove it?

At a glance, it looks like it might be down to 
intel_iommu_remove_device() not calling dmar_remove_one_dev_info() like 
the old notifier did. If the group is getting torn down and recreated, 
but the driver still has a stale pointer to the old default domain 
cached, which dmar_insert_one_dev_info() finds and returns, that would 
seem to explain the observed behaviour.

Robin.