linux-kernel - Re: Warning from AMD IOMMU performance counters

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Date:	Mon, 22 Feb 2016 17:36:09 -0800
From:	Laura Abbott <labbott@...hat.com>
To:	Wan Zongshun <vw@...mu.org>, Joerg Roedel <joro@...tes.org>,
	Suravee.Suthikulpanit@....com
Cc:	iommu@...ts.linux-foundation.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Warning from AMD IOMMU performance counters

On 02/21/2016 05:52 PM, Wan Zongshun wrote:
>
>
> -------- Original Message --------
>> Hi,
>>
>> Since about 4.4, we've been seeing reports of this warning on every boot
>> from some users:
>>
>> WARNING: CPU: 2 PID: 1 at drivers/iommu/amd_iommu_init.c:2301
>> amd_iommu_pc_get_set_reg_val+0xa8/0xe0()
>> Modules linked in:
>> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.2-300.fc23.x86_64 #1
>> Hardware name: Hewlett-Packard HP EliteBook 755 G2/221C, BIOS M84 Ver.
>> 01.10 10/20/2015
>>   0000000000000000 0000000026124b43 ffff88042d687d20 ffffffff813b0c9f
>>   0000000000000000 ffff88042d687d58 ffffffff810a2f12 ffff88042f014800
>>   0000000000000040 0000000000000000 ffffffff81d6c73d 0000000000000000
>> Call Trace:
>>   [<ffffffff813b0c9f>] dump_stack+0x44/0x55
>>   [<ffffffff810a2f12>] warn_slowpath_common+0x82/0xc0
>>   [<ffffffff81d6c73d>] ? memblock_find_dma_reserve+0x16a/0x16a
>>   [<ffffffff810a305a>] warn_slowpath_null+0x1a/0x20
>>   [<ffffffff814d3f48>] amd_iommu_pc_get_set_reg_val+0xa8/0xe0
>>   [<ffffffff81dafda7>] iommu_go_to_state+0x4d6/0x1384
>>   [<ffffffff813c02ea>] ? kvasprintf+0x7a/0xa0
>>   [<ffffffff81d6c73d>] ? memblock_find_dma_reserve+0x16a/0x16a
>>   [<ffffffff81db0cbd>] amd_iommu_init+0x13/0x201
>>   [<ffffffff81d6c74f>] pci_iommu_init+0x12/0x3c
>>   [<ffffffff81002123>] do_one_initcall+0xb3/0x200
>>   [<ffffffff810c0935>] ? parse_args+0x295/0x4b0
>>   [<ffffffff81d621c8>] kernel_init_freeable+0x189/0x223
>>   [<ffffffff8178dc00>] ? rest_init+0x80/0x80
>>   [<ffffffff8178dc0e>] kernel_init+0xe/0xe0
>>   [<ffffffff81799c8f>] ret_from_fork+0x3f/0x70
>>   [<ffffffff8178dc00>] ? rest_init+0x80/0x80
>>
>> Full bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=1310258
>>
>> Any idea what might be causing this spew?
>
> I also see this warning.
>
> Suravee's the one of this patch series might be fix this issue, you can try it.
>
> [PATCH V4 0/6] perf/amd/iommu: Enable multi-IOMMU support
>
>

That patch had other dependencies. I brought what I thought were enough of
them in to at least compile for the reporter to test (perf_event changes
from Borislav Petkov). Apparently the kernel doesn't boot with the series
so suspect there is an integration issue somewhere. I'm going to see if
I can more information from the reporter about what exactly went wrong
to see if I need more dependencies.

It would be nice to get a single patch which could be applied to stable.
Tainting the kernel immediately on bootup makes sorting through problems
more difficult.

Thanks,
Laura