linux-kernel - Re: ioatdma(Intel(R) I/OAT DMA Engine init failed)

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Date:	Thu, 19 May 2016 11:18:44 +0800
From:	Gavin Guo <gavin.guo@...onical.com>
To:	"Jiang, Dave" <dave.jiang@...el.com>
Cc:	"Koul, Vinod" <vinod.koul@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: ioatdma(Intel(R) I/OAT DMA Engine init failed)

On Thu, May 19, 2016 at 12:49 AM, Jiang, Dave <dave.jiang@...el.com> wrote:
> On Wed, 2016-05-18 at 13:27 +0000, Gavin Guo wrote:
>> On Tue, May 17, 2016 at 6:06 PM, Vinod Koul <vinod.koul@...el.com>
>> wrote:
>> >
>> > On Mon, May 16, 2016 at 06:08:20PM +0800, Gavin Guo wrote:
>> > >
>> > > The following error messages can be observed on the Intel
>> > > Haswell-E
>> > > chipset with v3.13 kernel. After the analysis, I found there is
>> > > no
>> > > difference in the logic of these error messages in the current
>> > > upstream kernel. I also searched the git log and can't find any
>> > > commit
>> > > which is fix to the error(correct me if I am wrong). The
>> > > following is
>> > > the detail, and I'll really appreciate if there is any comment.
>> > > :)
>> > 3.13 is ancient, can you check this on latest kernel
>> Thank you for the comment. It's running on the production system.
>> However,
>> I'll try to figure out if it's possible to test the latest kernel.
>
> I wonder if you don't have the extended PCI config space access enabled
> in your kernel config.

Really thanks for your advice. :)

I searched the internet about the extended PCI config space and found
the link:

[Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in
http://lwn.net/Articles/263288/

And I checked the config and found the CONFIG_PCI_MMCONFIG=y. The
following string also can be observed in the dmesg:

[    1.419853] PCI: MMCONFIG for domain 0000 [bus 00-ff] at
[mem0x80000000-0x8fffffff] (base 0x80000000)
[    1.419855] PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved in E820

It seems the extended PCI config space is enabled. If there is
anything missed?

>
>>
>> >
>> >
>> > >
>> > >
>> > > ioatdma 0000:00:04.0: channel error register unreachable
>> > > ioatdma 0000:00:04.0: channel enumeration error
>> > > ioatdma 0000:00:04.0: Intel(R) I/OAT DMA Engine init failed
>> > > ioatdma 0000:00:04.1: channel error register unreachable
>> > > ioatdma 0000:00:04.1: channel enumeration error
>> > > ioatdma 0000:00:04.1: Intel(R) I/OAT DMA Engine init failed
>> > > ...
>> > > ioatdma 0000:00:04.7: channel error register unreachable
>> > > ioatdma 0000:00:04.7: channel enumeration error
>> > > ioatdma 0000:00:04.7: Intel(R) I/OAT DMA Engine init failed
>> > > mei_me 0000:00:16.0: initialization failed.
>> > >
>> > > There are 8 I/OAT DMA controllers on the Haswell-E chipset:
>> > > 8086:2f20 ~ 8086:2f27
>> > > 80:04.0 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 0 (rev 02)
>> > > 80:04.1 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 1 (rev 02)
>> > > 80:04.2 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 2 (rev 02)
>> > > 80:04.3 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 3 (rev 02)
>> > > 80:04.4 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 4 (rev 02)
>> > > 80:04.5 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 5 (rev 02)
>> > > 80:04.6 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 6 (rev 02)
>> > > 80:04.7 System peripheral: Intel Corporation Haswell-E DMA
>> > > Channel 7 (rev 02)
>> > >
>> > > Analysis:
>> > > The bug happens when the driver is resetting DMA controller, this
>> > > is
>> > > the sequence: The function, ioat_pci_probe, is called when the
>> > > DMA
>> > > controller is detected by the PCI bus. Then,
>> > > ioat3_dma_probe -> ioat_probe -> ioat2_enumerate_channels ->
>> > > ioat3_reset_hw. The following code can be found in the
>> > > ioat3_reset_hw:
>> > >
>> > > drivers/dma/ioat/dma_v3.c:
>> > >         chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
>> > >         writel(chanerr, chan->reg_base + IOAT_CHANERR_OFFSET);
>> > > ...
>> > >         err = pci_read_config_dword(pdev,
>> > > IOAT_PCI_CHANERR_INT_OFFSET, &chanerr);
>> > > if (err) {
>> > > dev_err(&pdev->dev,
>> > > "channel error register unreachable\n");
>> > > return err;
>> > > }
>> > >
>> > > Obviously, there are something wrong in the channel error
>> > > register
>> > > reset process. Then all the way back to ioat_probe(). Because the
>> > > error happens, the dma->chancnt will be set to 0:
>> > >
>> > > drivers/dma/ioat/dma.c:
>> > >         if (!dma->chancnt) {
>> > >                 dev_err(dev, "channel enumeration error\n");
>> > >                 goto err_setup_interrupts;
>> > >         }
>> > >
>> > > Finally back to ioat_pci_probe:
>> > >
>> > > drivers/dma/ioat/pci.c:
>> > >                 err = ioat3_dma_probe(device, ioat_dca_enabled);
>> > >         else
>> > >                 return -ENODEV;
>> > >
>> > >         if (err) {
>> > >                 dev_err(dev, "Intel(R) I/OAT DMA Engine init
>> > > failed\n");
>> > >                 return -ENODEV;
>> > --
>> > ~Vinod

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