RE: 2.6.22-rc6-mm1 Intel DMAR crash on AMD x86_64

["Li, Shaohua" <shaohua.li@intel.com>]

>-----Original Message-----
>From: Robert Hancock [mailto:hancockr@shaw.ca]
>Sent: Friday, June 29, 2007 8:59 AM
>To: Zan Lynx
>Cc: Andrew Morton; linux-kernel@vger.kernel.org; Raj, Ashok; Li,
Shaohua;
>Keshavamurthy, Anil S
>Subject: Re: 2.6.22-rc6-mm1 Intel DMAR crash on AMD x86_64
>
>Zan Lynx wrote:
>> On Thu, 2007-06-28 at 03:43 -0700, Andrew Morton wrote:
>>>
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-
>rc6/2.6.22-rc6-mm1/
>>
>>> +intel-iommu-dmar-detection-and-parsing-logic.patch
>>> +intel-iommu-pci-generic-helper-function.patch
>>> +intel-iommu-pci-generic-helper-function-fix.patch
>>> +intel-iommu-clflush_cache_range-now-takes-size-param.patch
>>> +intel-iommu-iova-allocation-and-management-routines.patch
>>> +intel-iommu-iova-allocation-and-management-routines-fix.patch
>>> +intel-iommu-iova-allocation-and-management-routines-fix-2.patch
>>> +intel-iommu-intel-iommu-driver.patch
>>> +intel-iommu-intel-iommu-driver-fix.patch
>>> +intel-iommu-intel-iommu-driver-fix-2.patch
>>>
+intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
>>> +intel-iommu-intel-iommu-cmdline-option-forcedac.patch
>>> +intel-iommu-dmar-fault-handling-support.patch
>>> +intel-iommu-iommu-gfx-workaround.patch
>>> +intel-iommu-iommu-floppy-workaround.patch
>>> +intel-iommu-iommu-floppy-workaround-fix.patch
>>> +intel-iommu-iommu-floppy-workaround-fix-fix.patch
>>>
>>>  Intel IOMMU support
>>
>> I believe the above patch set is causing the problem.  On my first
try
>> with rc6-mm1 I said Yes to the CONFIG_DMAR options. (I'm nearly as
good
>> as random option selection :-)
>>
>> The system panicked during boot, I believe it was trying to detect an
>> Intel IOMMU.  Later when I have a camera, I will try to post a
>> screenshot of the backtrace. (I can't seem to get netconsole to work
on
>> boot, only in a module).
>>
>> When I recompiled without DMAR set, things seem to be working great.
I
>> seem to be getting better disk read throughput than rc3-mm1, by the
way.
>>
>> This laptop is an AMD Athlon64 on a NForce3 running a 64-bit Gentoo
>> build.
>>
>> I'll provide more details on request, and when I get the chance.
This
>> is a heads-up on the BUG in case someone has an "ah ha!" moment.
>
>I took a picture of it, looks like the backtrace is:
>
>NULL pointer dereference at 024
>EIP:dmar_table_init+0x11
>intel_iommu_init+0x30
>pci_iommu_init+0xe
>kernel_init+0x16e
>
>Presumably something is NULL in dmar_table_init that wasn't expected to
>be.. I would guess it likely crashes on any system without an Intel
>IOMMU in it.
How about something like below?


int __init dmar_table_init(void)
{
+	if (!dmar_tbl)
+		return -ENODEV;
	parse_dmar_table();
	if (list_empty(&dmar_drhd_units)) {
		printk(KERN_ERR PREFIX "No DMAR devices found\n");
		return -ENODEV;
	}
	return 0;
}
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