Message-ID: <ZU3SSClU6Ijn3M7B@nanopsycho>
Date: Fri, 10 Nov 2023 07:48:40 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Michalik, Michal" <michal.michalik@...el.com>,
	"Olech, Milena" <milena.olech@...el.com>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	"kuba@...nel.org" <kuba@...nel.org>
Subject: Re: [PATCH net 0/3] dpll: fix unordered unbind/bind registerer issues

Fri, Nov 10, 2023 at 12:35:43AM CET, arkadiusz.kubalewski@...el.com wrote:
>>From: Jiri Pirko <jiri@...nulli.us>
>>Sent: Thursday, November 9, 2023 7:07 PM
>>
>>Thu, Nov 09, 2023 at 06:20:14PM CET, arkadiusz.kubalewski@...el.com wrote:
>>>>From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
>>>>Sent: Thursday, November 9, 2023 11:51 AM
>>>>
>>>>On 08/11/2023 10:32, Arkadiusz Kubalewski wrote:
>>>>> Fix issues when performing unordered unbind/bind of a kernel modules
>>>>> which are using a dpll device with DPLL_PIN_TYPE_MUX pins.
>>>>> Currently only serialized bind/unbind of such use case works, fix
>>>>> the issues and allow for unserialized kernel module bind order.
>>>>>
>>>>> The issues are observed on the ice driver, i.e.,
>>>>>
>>>>> $ echo 0000:af:00.0 > /sys/bus/pci/drivers/ice/unbind
>>>>> $ echo 0000:af:00.1 > /sys/bus/pci/drivers/ice/unbind
>>>>>
>>>>> results in:
>>>>>
>>>>> ice 0000:af:00.0: Removed PTP clock
>>>>> BUG: kernel NULL pointer dereference, address: 0000000000000010
>>>>> PF: supervisor read access in kernel mode
>>>>> PF: error_code(0x0000) - not-present page
>>>>> PGD 0 P4D 0
>>>>> Oops: 0000 [#1] PREEMPT SMP PTI
>>>>> CPU: 7 PID: 71848 Comm: bash Kdump: loaded Not tainted 6.6.0-rc5_next-
>>>>>queue_19th-Oct-2023-01625-g039e5d15e451 #1
>>>>> Hardware name: Intel Corporation S2600STB/S2600STB, BIOS
>>>>>SE5C620.86B.02.01.0008.031920191559 03/19/2019
>>>>> RIP: 0010:ice_dpll_rclk_state_on_pin_get+0x2f/0x90 [ice]
>>>>> Code: 41 57 4d 89 cf 41 56 41 55 4d 89 c5 41 54 55 48 89 f5 53 4c 8b 66
>>>>>08 48 89 cb 4d 8d b4 24 f0 49 00 00 4c 89 f7 e8 71 ec 1f c5 <0f> b6 5b
>>>>>10
>>>>>41 0f b6 84 24 30 4b 00 00 29 c3 41 0f b6 84 24 28 4b
>>>>> RSP: 0018:ffffc902b179fb60 EFLAGS: 00010246
>>>>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
>>>>> RDX: ffff8882c1398000 RSI: ffff888c7435cc60 RDI: ffff888c7435cb90
>>>>> RBP: ffff888c7435cc60 R08: ffffc902b179fbb0 R09: 0000000000000000
>>>>> R10: ffff888ef1fc8050 R11: fffffffffff82700 R12: ffff888c743581a0
>>>>> R13: ffffc902b179fbb0 R14: ffff888c7435cb90 R15: 0000000000000000
>>>>> FS:  00007fdc7dae0740(0000) GS:ffff888c105c0000(0000)
>>>>>knlGS:0000000000000000
>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> CR2: 0000000000000010 CR3: 0000000132c24002 CR4: 00000000007706e0
>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> PKRU: 55555554
>>>>> Call Trace:
>>>>>   <TASK>
>>>>>   ? __die+0x20/0x70
>>>>>   ? page_fault_oops+0x76/0x170
>>>>>   ? exc_page_fault+0x65/0x150
>>>>>   ? asm_exc_page_fault+0x22/0x30
>>>>>   ? ice_dpll_rclk_state_on_pin_get+0x2f/0x90 [ice]
>>>>>   ? __pfx_ice_dpll_rclk_state_on_pin_get+0x10/0x10 [ice]
>>>>>   dpll_msg_add_pin_parents+0x142/0x1d0
>>>>>   dpll_pin_event_send+0x7d/0x150
>>>>>   dpll_pin_on_pin_unregister+0x3f/0x100
>>>>>   ice_dpll_deinit_pins+0xa1/0x230 [ice]
>>>>>   ice_dpll_deinit+0x29/0xe0 [ice]
>>>>>   ice_remove+0xcd/0x200 [ice]
>>>>>   pci_device_remove+0x33/0xa0
>>>>>   device_release_driver_internal+0x193/0x200
>>>>>   unbind_store+0x9d/0xb0
>>>>>   kernfs_fop_write_iter+0x128/0x1c0
>>>>>   vfs_write+0x2bb/0x3e0
>>>>>   ksys_write+0x5f/0xe0
>>>>>   do_syscall_64+0x59/0x90
>>>>>   ? filp_close+0x1b/0x30
>>>>>   ? do_dup2+0x7d/0xd0
>>>>>   ? syscall_exit_work+0x103/0x130
>>>>>   ? syscall_exit_to_user_mode+0x22/0x40
>>>>>   ? do_syscall_64+0x69/0x90
>>>>>   ? syscall_exit_work+0x103/0x130
>>>>>   ? syscall_exit_to_user_mode+0x22/0x40
>>>>>   ? do_syscall_64+0x69/0x90
>>>>>   entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>>>>> RIP: 0033:0x7fdc7d93eb97
>>>>> Code: 0b 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e
>>>>>fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0
>>>>>ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
>>>>> RSP: 002b:00007fff2aa91028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
>>>>> RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007fdc7d93eb97
>>>>> RDX: 000000000000000d RSI: 00005644814ec9b0 RDI: 0000000000000001
>>>>> RBP: 00005644814ec9b0 R08: 0000000000000000 R09: 00007fdc7d9b14e0
>>>>> R10: 00007fdc7d9b13e0 R11: 0000000000000246 R12: 000000000000000d
>>>>> R13: 00007fdc7d9fb780 R14: 000000000000000d R15: 00007fdc7d9f69e0
>>>>>   </TASK>
>>>>> Modules linked in: uinput vfio_pci vfio_pci_core vfio_iommu_type1 vfio
>>>>>irqbypass ixgbevf snd_seq_dummy snd_hrtimer snd_seq snd_timer
>>>>>snd_seq_device snd soundcore overlay qrtr rfkill vfat fat xfs libcrc32c
>>>>>rpcrdma sunrpc rdma_ucm ib_srpt ib_isert iscsi_target_mod
>>>>>target_core_mod
>>>>>ib_iser libiscsi scsi_transport_iscsi rdma_cm iw_cm ib_cm intel_rapl_msr
>>>>>intel_rapl_common intel_uncore_frequency intel_uncore_frequency_common
>>>>>isst_if_common skx_edac nfit libnvdimm ipmi_ssif x86_pkg_temp_thermal
>>>>>intel_powerclamp coretemp irdma rapl intel_cstate ib_uverbs iTCO_wdt
>>>>>iTCO_vendor_support acpi_ipmi intel_uncore mei_me ipmi_si pcspkr
>>>>>i2c_i801
>>>>>ib_core mei ipmi_devintf intel_pch_thermal ioatdma i2c_smbus
>>>>>ipmi_msghandler lpc_ich joydev acpi_power_meter acpi_pad ext4 mbcache
>>>>>jbd2
>>>>>sd_mod t10_pi sg ast i2c_algo_bit drm_shmem_helper drm_kms_helper ice
>>>>>crct10dif_pclmul ixgbe crc32_pclmul drm crc32c_intel ahci i40e libahci
>>>>>ghash_clmulni_intel libata mdio dca gnss wmi fuse [last unloaded: iavf]
>>>>> CR2: 0000000000000010
>>>>>
>>>>> Arkadiusz Kubalewski (3):
>>>>>    dpll: fix pin dump crash after module unbind
>>>>>    dpll: fix pin dump crash for rebound module
>>>>>    dpll: fix register pin with unregistered parent pin
>>>>>
>>>>>   drivers/dpll/dpll_core.c    |  8 ++------
>>>>>   drivers/dpll/dpll_core.h    |  4 ++--
>>>>>   drivers/dpll/dpll_netlink.c | 37 ++++++++++++++++++++++--------------
>>>>>-
>>>>>   3 files changed, 26 insertions(+), 23 deletions(-)
>>>>>
>>>>
>>>>
>>>>I still don't get how can we end up with unregistered pin. And shouldn't
>>>>drivers do unregister of dpll/pin during release procedure? I thought it
>>>>was kind of agreement we reached while developing the subsystem.
>>>>
>>>
>>>It's definitely not about ending up with unregistered pins.
>>>
>>>Usually the driver is loaded for PF0, PF1, PF2, PF3 and unloaded in
>>>opposite
>>>order: PF3, PF2, PF1, PF0. And this is working without any issues.
>>
>>Please fix this in the driver.
>>
>
>Thanks for your feedback, but this is already wrong advice.
>
>Our HW/FW is designed in different way than yours, it doesn't mean it is wrong.
>As you might recall from our sync meetings, the dpll subsystem is to unify
>approaches and reduce the code in the drivers, where your advice is exactly
>opposite, suggested fix would require to implement extra synchronization of the
>dpll and pin registration state between driver instances, most probably with
>use of additional modules like aux-bus or something similar, which was from the
>very beginning something we tried to avoid.
>Only ice uses the infrastructure of muxed pins, and this is broken as it
>doesn't allow unbind the driver which have registered dpll and pins without
>crashing the kernel, so a fix is required in dpll subsystem, not in the driver.

I replied in the other patch thread.


>
>Thank you!
>Arkadiusz
>
>>
>>>
>>>Above crash is caused because of unordered driver unload, where dpll
>>>subsystem
>>>tries to notify muxed pin was deleted, but at that time the parent is
>>>already
>>>gone, thus data points to memory which is no longer available, thus crash
>>>happens when trying to dump pin parents.
>>>
>>>This series fixes all issues I could find connected to the situation where
>>>muxed-pins are trying to access their parents, when parent registerer was
>>>removed
>>>in the meantime.
>>>
>>>Thank you!
>>>Arkadiusz

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