Date: Wed, 31 Jan 2024 13:25:29 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Yi Liu <yi.l.liu@...el.com>, baolu.lu@...ux.intel.com,
 bhelgaas@...gle.com, robin.murphy@....com, jgg@...pe.ca
Cc: kevin.tian@...el.com, dwmw2@...radead.org, will@...nel.org,
 lukas@...ner.de, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org, Haorong Ye <yehaorong@...edance.com>
Subject: Re: [PATCH v12 2/5] iommu/vt-d: don't issue ATS Invalidation request
 when device is disconnected

On 1/31/2024 12:25 PM, Yi Liu wrote:
> On 2024/1/30 13:37, Ethan Zhao wrote:
>>
>> On 1/29/2024 5:32 PM, Yi Liu wrote:
>>> On 2024/1/29 11:49, Ethan Zhao wrote:
>>>> For those endpoint devices connect to system via hotplug capable 
>>>> ports,
>>>> users could request a hot reset to the device by flapping device's 
>>>> link
>>>> through setting the slot's link control register, as pciehp_ist() 
>>>> DLLSC
>>>> interrupt sequence response, pciehp will unload the device driver and
>>>> then power it off. thus cause an IOMMU device-TLB invalidation (Intel
>>>> VT-d spec, or ATS Invalidation in PCIe spec r6.1) request for 
>>>> non-existence
>>>> target device to be sent and deadly loop to retry that request 
>>>> after ITE
>>>> fault triggered in interrupt context.
>>>>
>>>> That would cause following continuous hard lockup warning and 
>>>> system hang
>>>>
>>>> [ 4211.433662] pcieport 0000:17:01.0: pciehp: Slot(108): Link Down
>>>> [ 4211.433664] pcieport 0000:17:01.0: pciehp: Slot(108): Card not 
>>>> present
>>>> [ 4223.822591] NMI watchdog: Watchdog detected hard LOCKUP on cpu 144
>>>> [ 4223.822622] CPU: 144 PID: 1422 Comm: irq/57-pciehp Kdump: loaded 
>>>> Tainted: G S
>>>>           OE    kernel version xxxx
>>>> [ 4223.822623] Hardware name: vendorname xxxx 666-106,
>>>> BIOS 01.01.02.03.01 05/15/2023
>>>> [ 4223.822623] RIP: 0010:qi_submit_sync+0x2c0/0x490
>>>> [ 4223.822624] Code: 48 be 00 00 00 00 00 08 00 00 49 85 74 24 20 
>>>> 0f 95 c1 48 8b
>>>>   57 10 83 c1 04 83 3c 1a 03 0f 84 a2 01 00 00 49 8b 04 24 8b 70 34 
>>>> <40> f6 c6 1
>>>> 0 74 17 49 8b 04 24 8b 80 80 00 00 00 89 c2 d3 fa 41 39
>>>> [ 4223.822624] RSP: 0018:ffffc4f074f0bbb8 EFLAGS: 00000093
>>>> [ 4223.822625] RAX: ffffc4f040059000 RBX: 0000000000000014 RCX: 
>>>> 0000000000000005
>>>> [ 4223.822625] RDX: ffff9f3841315800 RSI: 0000000000000000 RDI: 
>>>> ffff9f38401a8340
>>>> [ 4223.822625] RBP: ffff9f38401a8340 R08: ffffc4f074f0bc00 R09: 
>>>> 0000000000000000
>>>> [ 4223.822626] R10: 0000000000000010 R11: 0000000000000018 R12: 
>>>> ffff9f384005e200
>>>> [ 4223.822626] R13: 0000000000000004 R14: 0000000000000046 R15: 
>>>> 0000000000000004
>>>> [ 4223.822626] FS:  0000000000000000(0000) GS:ffffa237ae400000(0000)
>>>> knlGS:0000000000000000
>>>> [ 4223.822627] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 4223.822627] CR2: 00007ffe86515d80 CR3: 000002fd3000a001 CR4: 
>>>> 0000000000770ee0
>>>> [ 4223.822627] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
>>>> 0000000000000000
>>>> [ 4223.822628] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 
>>>> 0000000000000400
>>>> [ 4223.822628] PKRU: 55555554
>>>> [ 4223.822628] Call Trace:
>>>> [ 4223.822628]  qi_flush_dev_iotlb+0xb1/0xd0
>>>> [ 4223.822628]  __dmar_remove_one_dev_info+0x224/0x250
>>>> [ 4223.822629]  dmar_remove_one_dev_info+0x3e/0x50
>>>> [ 4223.822629]  intel_iommu_release_device+0x1f/0x30
>>>> [ 4223.822629]  iommu_release_device+0x33/0x60
>>>> [ 4223.822629]  iommu_bus_notifier+0x7f/0x90
>>>> [ 4223.822630]  blocking_notifier_call_chain+0x60/0x90
>>>> [ 4223.822630]  device_del+0x2e5/0x420
>>>> [ 4223.822630]  pci_remove_bus_device+0x70/0x110
>>>> [ 4223.822630]  pciehp_unconfigure_device+0x7c/0x130
>>>> [ 4223.822631]  pciehp_disable_slot+0x6b/0x100
>>>> [ 4223.822631] pciehp_handle_presence_or_link_change+0xd8/0x320
>>>> [ 4223.822631]  pciehp_ist+0x176/0x180
>>>> [ 4223.822631]  ? irq_finalize_oneshot.part.50+0x110/0x110
>>>> [ 4223.822632]  irq_thread_fn+0x19/0x50
>>>> [ 4223.822632]  irq_thread+0x104/0x190
>>>> [ 4223.822632]  ? irq_forced_thread_fn+0x90/0x90
>>>> [ 4223.822632]  ? irq_thread_check_affinity+0xe0/0xe0
>>>> [ 4223.822633]  kthread+0x114/0x130
>>>> [ 4223.822633]  ? __kthread_cancel_work+0x40/0x40
>>>> [ 4223.822633]  ret_from_fork+0x1f/0x30
>>>> [ 4223.822633] Kernel panic - not syncing: Hard LOCKUP
>>>> [ 4223.822634] CPU: 144 PID: 1422 Comm: irq/57-pciehp Kdump: loaded 
>>>> Tainted: G S
>>>>           OE     kernel version xxxx
>>>> [ 4223.822634] Hardware name: vendorname xxxx 666-106,
>>>> BIOS 01.01.02.03.01 05/15/2023
>>>> [ 4223.822634] Call Trace:
>>>> [ 4223.822634]  <NMI>
>>>> [ 4223.822635]  dump_stack+0x6d/0x88
>>>> [ 4223.822635]  panic+0x101/0x2d0
>>>> [ 4223.822635]  ? ret_from_fork+0x11/0x30
>>>> [ 4223.822635]  nmi_panic.cold.14+0xc/0xc
>>>> [ 4223.822636]  watchdog_overflow_callback.cold.8+0x6d/0x81
>>>> [ 4223.822636]  __perf_event_overflow+0x4f/0xf0
>>>> [ 4223.822636]  handle_pmi_common+0x1ef/0x290
>>>> [ 4223.822636]  ? __set_pte_vaddr+0x28/0x40
>>>> [ 4223.822637]  ? flush_tlb_one_kernel+0xa/0x20
>>>> [ 4223.822637]  ? __native_set_fixmap+0x24/0x30
>>>> [ 4223.822637]  ? ghes_copy_tofrom_phys+0x70/0x100
>>>> [ 4223.822637]  ? __ghes_peek_estatus.isra.16+0x49/0xa0
>>>> [ 4223.822637]  intel_pmu_handle_irq+0xba/0x2b0
>>>> [ 4223.822638]  perf_event_nmi_handler+0x24/0x40
>>>> [ 4223.822638]  nmi_handle+0x4d/0xf0
>>>> [ 4223.822638]  default_do_nmi+0x49/0x100
>>>> [ 4223.822638]  exc_nmi+0x134/0x180
>>>> [ 4223.822639]  end_repeat_nmi+0x16/0x67
>>>> [ 4223.822639] RIP: 0010:qi_submit_sync+0x2c0/0x490
>>>> [ 4223.822639] Code: 48 be 00 00 00 00 00 08 00 00 49 85 74 24 20 
>>>> 0f 95 c1 48 8b
>>>>   57 10 83 c1 04 83 3c 1a 03 0f 84 a2 01 00 00 49 8b 04 24 8b 70 34 
>>>> <40> f6 c6 10
>>>>   74 17 49 8b 04 24 8b 80 80 00 00 00 89 c2 d3 fa 41 39
>>>> [ 4223.822640] RSP: 0018:ffffc4f074f0bbb8 EFLAGS: 00000093
>>>> [ 4223.822640] RAX: ffffc4f040059000 RBX: 0000000000000014 RCX: 
>>>> 0000000000000005
>>>> [ 4223.822640] RDX: ffff9f3841315800 RSI: 0000000000000000 RDI: 
>>>> ffff9f38401a8340
>>>> [ 4223.822641] RBP: ffff9f38401a8340 R08: ffffc4f074f0bc00 R09: 
>>>> 0000000000000000
>>>> [ 4223.822641] R10: 0000000000000010 R11: 0000000000000018 R12: 
>>>> ffff9f384005e200
>>>> [ 4223.822641] R13: 0000000000000004 R14: 0000000000000046 R15: 
>>>> 0000000000000004
>>>> [ 4223.822641]  ? qi_submit_sync+0x2c0/0x490
>>>> [ 4223.822642]  ? qi_submit_sync+0x2c0/0x490
>>>> [ 4223.822642]  </NMI>
>>>> [ 4223.822642]  qi_flush_dev_iotlb+0xb1/0xd0
>>>> [ 4223.822642]  __dmar_remove_one_dev_info+0x224/0x250
>>>> [ 4223.822643]  dmar_remove_one_dev_info+0x3e/0x50
>>>> [ 4223.822643]  intel_iommu_release_device+0x1f/0x30
>>>> [ 4223.822643]  iommu_release_device+0x33/0x60
>>>> [ 4223.822643]  iommu_bus_notifier+0x7f/0x90
>>>> [ 4223.822644]  blocking_notifier_call_chain+0x60/0x90
>>>> [ 4223.822644]  device_del+0x2e5/0x420
>>>> [ 4223.822644]  pci_remove_bus_device+0x70/0x110
>>>> [ 4223.822644]  pciehp_unconfigure_device+0x7c/0x130
>>>> [ 4223.822644]  pciehp_disable_slot+0x6b/0x100
>>>> [ 4223.822645] pciehp_handle_presence_or_link_change+0xd8/0x320
>>>> [ 4223.822645]  pciehp_ist+0x176/0x180
>>>> [ 4223.822645]  ? irq_finalize_oneshot.part.50+0x110/0x110
>>>> [ 4223.822645]  irq_thread_fn+0x19/0x50
>>>> [ 4223.822646]  irq_thread+0x104/0x190
>>>> [ 4223.822646]  ? irq_forced_thread_fn+0x90/0x90
>>>> [ 4223.822646]  ? irq_thread_check_affinity+0xe0/0xe0
>>>> [ 4223.822646]  kthread+0x114/0x130
>>>> [ 4223.822647]  ? __kthread_cancel_work+0x40/0x40
>>>> [ 4223.822647]  ret_from_fork+0x1f/0x30
>>>> [ 4223.822647] Kernel Offset: 0x6400000 from 0xffffffff81000000 
>>>> (relocation
>>>> range: 0xffffffff80000000-0xffffffffbfffffff)
>>>>
>>>> Such issue could be triggered by all kinds of regular surprise removal
>>>> hotplug operation. like:
>>>>
>>>> 1. pull EP(endpoint device) out directly.
>>>> 2. turn off EP's power.
>>>> 3. bring the link down.
>>>> etc.
>>>>
>>>> this patch aims to work for regular safe removal and surprise removal
>>>> unplug. these hot unplug handling process could be optimized for 
>>>> fix the
>>>> ATS Invalidation hang issue by calling pci_dev_is_disconnected() in
>>>> function devtlb_invalidation_with_pasid() to check target device 
>>>> state to
>>>> avoid sending meaningless ATS Invalidation request to iommu when 
>>>> device is
>>>> gone. (see IMPLEMENTATION NOTE in PCIe spec r6.1 section 10.3.1)
>>>>
>>>> For safe removal, device wouldn't be removed until the whole software
>>>> handling process is done, it wouldn't trigger the hard lock up issue
>>>> caused by too long ATS Invalidation timeout wait. In safe removal 
>>>> path,
>>>> device state isn't set to pci_channel_io_perm_failure in
>>>> pciehp_unconfigure_device() by checking 'presence' parameter, calling
>>>> pci_dev_is_disconnected() in devtlb_invalidation_with_pasid() will 
>>>> return
>>>> false there, wouldn't break the function.
>>>>
>>>> For surprise removal, device state is set to 
>>>> pci_channel_io_perm_failure in
>>>> pciehp_unconfigure_device(), means device is already gone 
>>>> (disconnected)
>>>> call pci_dev_is_disconnected() in devtlb_invalidation_with_pasid() 
>>>> will
>>>> return true to break the function not to send ATS Invalidation 
>>>> request to
>>>> the disconnected device blindly, thus avoid to trigger further ITE 
>>>> fault,
>>>> and ITE fault will block all invalidation request to be handled.
>>>> furthermore retry the timeout request could trigger hard lockup.
>>>>
>>>> safe removal (present) & surprise removal (not present)
>>>>
>>>> pciehp_ist()
>>>>     pciehp_handle_presence_or_link_change()
>>>>       pciehp_disable_slot()
>>>>         remove_board()
>>>>           pciehp_unconfigure_device(presence) {
>>>>             if (!presence)
>>>>                  pci_walk_bus(parent, pci_dev_set_disconnected, NULL);
>>>>             }
>>>>
>>>> this patch works for regular safe removal and surprise removal of ATS
>>>> capable endpoint on PCIe switch downstream ports.
>>>
>>> this is not the real fix. So this series may focus on the real fix 
>>> (avoid
>>> dead loop in intel iommu driver when ITE happens), and in the end 
>>> add this
>>> patch as an optimization.
>>
>> This is the second time I brought it on top of other patches as Baolu 
>> perfers
>>
>> Bjorn also suggested to take this one as optimization addition to 
>> others.
>>
>> Anyway, just the order in this patch list, the same result after 
>> applied.
>>
>> to solve customer issue, this one is needed.
>
> I think even without this patch, customer's issue can be fixed by the 
> last
> 3 patches of this series. is it? So this patch is not the real fix 
> customer
> wants, but nice to have. That's why I think it is an optimization. The
> result is the same after applying in mainline. It's fine to keep it the
> first two of this series, but need to tell customer what kind of patches
> need to be back-ported.

The timeout threshold of hard lockup watchdog could be configured by user via
sysctl sysfs etc, I am not 100% sure the handling after ITE could suppress all
user's hard lockup warning.

So avoid to be trapped into fault handling is still the first choice in my
opinion.

Thanks,
Ethan

>
> Regards,
> Yi Liu
>
>>
>>>
>>>> Fixes: 6f7db75e1c46 ("iommu/vt-d: Add second level page table 
>>>> interface")
>>>> Tested-by: Haorong Ye <yehaorong@...edance.com>
>>>> Signed-off-by: Ethan Zhao <haifeng.zhao@...ux.intel.com>
>>>> ---
>>>>   drivers/iommu/intel/pasid.c | 3 +++
>>>>   1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
>>>> index 3239cefa4c33..953592125e4a 100644
>>>> --- a/drivers/iommu/intel/pasid.c
>>>> +++ b/drivers/iommu/intel/pasid.c
>>>> @@ -214,6 +214,9 @@ devtlb_invalidation_with_pasid(struct 
>>>> intel_iommu *iommu,
>>>>       if (!info || !info->ats_enabled)
>>>>           return;
>>>>   +    if (pci_dev_is_disconnected(to_pci_dev(dev)))
>>>> +        return;
>>>> +
>>>>       sid = info->bus << 8 | info->devfn;
>>>>       qdep = info->ats_qdep;
>>>>       pfsid = info->pfsid;
>>>

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