Date:	Thu, 21 Jan 2016 16:02:19 +0800
From:	Chen Fan <chen.fan.fnst@...fujitsu.com>
To:	Bjorn Helgaas <helgaas@...nel.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lenb@...nel.org>, <izumi.taku@...fujitsu.com>,
	<wency@...fujitsu.com>, <caoj.fnst@...fujitsu.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Jiang Liu <jiang.liu@...ux.intel.com>
Subject: Re: [PATCH] pci: fix unavailable irq number 255 reported by BIOS


On 01/21/2016 01:12 AM, Bjorn Helgaas wrote:
> On Wed, Jan 20, 2016 at 12:21:24PM +0800, Chen Fan wrote:
>> On 01/20/2016 08:24 AM, Bjorn Helgaas wrote:
>>> [+cc Jiang]
>>>
>>> Hi Chen,
>>>
>>> On Tue, Jan 19, 2016 at 02:43:30PM +0100, Rafael J. Wysocki wrote:
>>>> On Tuesday, January 19, 2016 09:45:13 AM Chen Fan wrote:
>>>>> In our environment, when enable Secure boot, we found an abnormal
>>> This has more information than necessary.  I don't think Secure Boot is
>>> really relevant, and nor are the timestamps and stack addresses below.
>> I just think enable the Secure Boot, probably the firmware assigned
>> a 0xff interrupt to the device which unauthenticated.
> The important thing is that you're changing the way we handle
> Interrupt Line being 0xff.  That affects more than just Secure Boot
> users.  It's fine to mention Secure Boot later, as one example of an
> affected scenario.
>
> I don't know anything about Secure Boot, but setting Interrupt Line to
> 0xff would obviously not be a robust way of hiding an unauthenticated
> device.  But it sounds like you're just speculating about that anyway.
>
>>>>> phenomenon as following call trace shows. after investigation, we
>>>>> found the firmware assigned an irq number 255 which means unknown
>>>>> or no connection in PCI local spec for i801_smbus, meanwhile the
>>>>> ACPI didn't configure the pci irq routing. and the 255 irq number
>>>>> was assigned for megasa msix without IRQF_SHARED. then in this case
>>>>> during i801_smbus probe, the i801_smbus driver would request irq with
>>>>> bad irq number 255. but the 255 irq number was assigned for memgasa
>>>>> with MSIX enable. which will cause request_irq fails, and call trace
>>>>> shows, actually, we should expose the error early, rather than in request
>>>>> irq, here we simply fix the problem by return err when find the irq is
>>>>> 255.
>>>>> See the call trace:
>>>>>
>>>>>   [   32.459195] ipmi device interface
>>>>>   [   32.612907] shpchp: Standard Hot Plug PCI Controller Driver version: 0.4
>>>>>   [   32.800459] ixgbe: Intel(R) 10 Gigabit PCI Express Network Driver - version 4.0.1-k-rh
>>>>>   [   32.818319] ixgbe: Copyright (c) 1999-2014 Intel Corporation.
>>>>>   [   32.844009] lpc_ich 0001:80:1f.0: I/O space for ACPI uninitialized
>>>>>   [   32.850093] i801_smbus 0000:00:1f.3: enabling device (0140 -> 0143)
>>>>>   [   32.851134] i801_smbus 0000:00:1f.3: can't derive routing for PCI INT C
>>>>>   [   32.851136] i801_smbus 0000:00:1f.3: PCI INT C: no GSI
>>>>>   [   32.851164] genirq: Flags mismatch irq 255. 00000080 (i801_smbus) vs. 00000000 (megasa
>>>>>   [   32.851168] CPU: 0 PID: 2487 Comm: kworker/0:1 Not tainted 3.10.0-229.el7.x86_64 #1
>>>>>   [   32.851170] Hardware name: FUJITSU PRIMEQUEST 2800E2/D3736, BIOS PRIMEQUEST 2000 Serie5
>>>>>   [   32.851178] Workqueue: events work_for_cpu_fn
>>>>>   [   32.851208]  ffff88086c330b00 00000000e233a9df ffff88086d57bca0 ffffffff81603f36
>>>>>   [   32.851227]  ffff88086d57bcf8 ffffffff8110d23a ffff88686fe02000 0000000000000246
>>>>>   [   32.851246]  ffff88086a9a8c00 00000000e233a9df ffffffffa00ad220 0000000000000080
>>>>>   [   32.851247] Call Trace:
>>>>>   [   32.851261]  [<ffffffff81603f36>] dump_stack+0x19/0x1b
>>>>>   [   32.851271]  [<ffffffff8110d23a>] __setup_irq+0x54a/0x570
>>>>>   [   32.851282]  [<ffffffffa00ad220>] ? i801_check_pre.isra.5+0xe0/0xe0 [i2c_i801]
>>>>>   [   32.851289]  [<ffffffff8110d3bc>] request_threaded_irq+0xcc/0x170
>>>>>   [   32.851298]  [<ffffffffa00ae87f>] i801_probe+0x32f/0x508 [i2c_i801]
>>>>>   [   32.851308]  [<ffffffff81308385>] local_pci_probe+0x45/0xa0
>>>>>   [   32.851315]  [<ffffffff8108bfd4>] work_for_cpu_fn+0x14/0x20
>>>>>   [   32.851323]  [<ffffffff8108f0ab>] process_one_work+0x17b/0x470
>>>>>   [   32.851330]  [<ffffffff81090003>] worker_thread+0x293/0x400
>>>>>   [   32.851338]  [<ffffffff8108fd70>] ? rescuer_thread+0x400/0x400
>>>>>   [   32.851346]  [<ffffffff8109726f>] kthread+0xcf/0xe0
>>>>>   [   32.851353]  [<ffffffff810971a0>] ? kthread_create_on_node+0x140/0x140
>>>>>   [   32.851362]  [<ffffffff81613cfc>] ret_from_fork+0x7c/0xb0
>>>>>   [   32.851369]  [<ffffffff810971a0>] ? kthread_create_on_node+0x140/0x140
>>>>>   [   32.851373] i801_smbus 0000:00:1f.3: Failed to allocate irq 255: -16
>>>>>   [   32.851435] i801_smbus: probe of 0000:00:1f.3 failed with error -16
>>> Since the Interrupt Line register is writable and might contain any
>>> value, it would be nice if Linux could at least tolerate anything
>>> firmware might leave there without a backtrace, even if we end up not
>>> being able to use the device.
>>>
>>> Your patch changes the acpi_pci_irq_enable() return value from 0 to
>>> -EINVAL for this case.  You're running v3.10, and this change probably
>>> makes pci_enable_device() fail.  I suppose the user-visible effect is
>>> that with your patch,
>>>
>>>    - there's no backtrace,
>>>    - i801_smbus fails with "Failed to enable SMBus PCI device" instead
>>>      of with "Failed to allocate irq 255", and
>>>    - i801_smbus fails even if no other device is using IRQ 255, instead
>>>      of "succeeding" and using an IRQ 255 that probably doesn't work
>>>      (this seems like maybe the most important difference)
>>>
>>> Jiang has changed this path with 890e4847587f ("PCI: Add
>>> pcibios_alloc_irq() and pcibios_free_irq()"), so I think on newer
>>> kernels, we'll never even call the i801_smbus probe function.
>> no, on newer kernels, this phenomenon also probably appearance,
>> with this patch 890e4847587f change, it didn't change the
>> acpi_pci_irq_enable() return value, with the problem it also return 0,
>> and then still call __pci_device_probe() to do i801_smbus probe
>> function in pci_device_probe() function.
> I meant that *with your patch*, newer kernels won't call the
> i801_smbus probe function.
>
>>> What behavior are you looking for from i801_smbus?  Decline to claim
>>> the device?  Try to use the device without interrupts?  Try to figure
>>> out an interrupt in some other way?
>> I think if BIOS assigned 0xff interrupt line to device, and kernel
>> can't look
>> up a valid interrupt for the device, we should not allow to use the device.
>>> I'm not 100% sure that 890e4847587f does the right thing by preventing
>>> a driver from claiming a device where we can't set up an IRQ.  It's
>>> conceivable that a driver could still operate a device even without an
>>> IRQ.
>> I don't understanding, does without IRQ for device still work?
> Polling drivers do not need IRQs.  The PCI core has no idea whether a
> driver is interrupt-driven or polling, so we can't assume that a
> device with no IRQ is useless.
Got it, I observed the smbus driver has changed to polling when request_irq
failed on new kernel.
can we use a broken_irq flag in pci_dev to mark the device irq if invalid ?
then if a device broken_irq set, we don't need to call request_irq and
directly return failure. of course, maybe we need to check this for all 
devices.

BTW, can we skip the 0xff irq number when allocating irq in x86 arch ?

Thanks,
Chen


>
> Bjorn
>
>
> .
>

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