linux-kernel - git-latest: kernel oops in IOMMU setup

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Message-ID: <20090108120538.0176d348@infradead.org>
Date:	Thu, 8 Jan 2009 12:05:38 -0800
From:	Dirk Hohndel <hohndel@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>, iommu@...ts.linux-foundation.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: git-latest: kernel oops in IOMMU setup

latest git from Linus. On a Thinkpad x200s with VT-d enabled (if I
disable VT-d, this of course goes away). 

The oops happens very early during boot in device_to_iommu (called
from domain_context_mapping_one).

Looking at the code dump and the disassembled function here's where
the error happens:

static struct intel_iommu *device_to_iommu(u8 bus, u8 devfn)
{
        struct dmar_drhd_unit *drhd = NULL;
        int i;

        for_each_drhd_unit(drhd) {
                if (drhd->ignored)
                        continue;

                for (i = 0; i < drhd->devices_cnt; i++)
                        if (drhd->devices[i]->bus->number == bus &&
--> drhd->devices[0] is NULL
                            drhd->devices[i]->devfn == devfn)
                                return drhd->iommu;

Given how early this happens it's a little hard to provide logs, etc. I
literally used delay_boot=100 and wrote things down by hand (forgot my
digital camera) and then added printk's to verify).

please let me know what other data I should collect.

The system ran fine with the 2.6.28 release kernel.

/D

-- 
Dirk Hohndel
Intel Open Source Technology Center
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