Re: [gentoo-user] CONFIG_IOMMU_SUPPORT???

[Mark Knecht <markknecht@gmail.com>]

On Wed, Aug 24, 2011 at 11:58 AM, Hilco Wijbenga
<hilco.wijbenga@gmail.com> wrote:
> On 24 August 2011 10:55, Mark Knecht <markknecht@gmail.com> wrote:
>> On Tue, Aug 23, 2011 at 9:18 PM, Hilco Wijbenga
>> <hilco.wijbenga@gmail.com> wrote:
>>> On 23 August 2011 20:38, Mark Knecht <markknecht@gmail.com> wrote:
>>>> Hi all,
>>>>   Can someone point me toward somehow enabling CONFIG_IOMMU_SUPPORT?
>>>> It is apparently a kernel config option no required by
>>>> virtualbox-drivers but I'm not finding it in the 3.0.3 kernel. I
>>>> suspect there's something else I need to enable before this option
>>>> becomes available? Unfortunately I haven't been able to Google what I
>>>> need to do to find it.
>>>>
>>>> Thanks,
>>>> Mark
>>>>
>>>> * Messages for package app-emulation/virtualbox-modules-4.1.2:
>>>>
>>>>  *   CONFIG_IOMMU_SUPPORT:       is not set when it should be.
>>>>  * Please check to make sure these options are set correctly.
>>>>  * Failure to do so may cause unexpected problems.
>>>> <SNIP>
>>>>
>>>> k2 linux # cat .config | grep IOMMU
>>>> CONFIG_GART_IOMMU=y
>>>> # CONFIG_CALGARY_IOMMU is not set
>>>> CONFIG_AMD_IOMMU=y
>>>> # CONFIG_AMD_IOMMU_STATS is not set
>>>> CONFIG_IOMMU_HELPER=y
>>>> CONFIG_IOMMU_API=y
>>>> # CONFIG_IOMMU_DEBUG is not set
>>>> # CONFIG_IOMMU_STRESS is not set
>>>> k2 linux #
>>>
>>> I noticed the same. There does not appear to be any such option but
>>> luckily its absence does not appear to affect running VB at all.
>>>
>>
>> At the time of writing this I haven't tried Gregory's item about the
>> CONFIG_CALGARY_IOMMU option. I'll try that later when I get to the
>> machine but the reading I did on the web sounded like that was for IBM
>> specific hardware.
>>
>> Here it seems that on the machine I was working - Intel based, i920 -
>> VB won't install Win 7 64-bit without it. I get a bunch of messages
>> that it will install but many cause problems. Are you running any
>> 64-bit VMs?
>
> Sort of. I'm working on installing Gentoo AMD64 in a VB machine. No
> problems so far but I've only just started (it's a weekend project).
> Certainly no Windows.
>
>> However I've got another Intel machine where I can install Win 7
>> 64-bit in VB just fine with no complaints at all. Here's the IOMMU
>> stuff from that box:
>>
>> mark@c2stable ~ $ uname -a
>> Linux c2stable 3.0.1-gentoo #1 SMP PREEMPT Mon Aug 8 13:05:19 PDT 2011
>> x86_64 Intel(R) Core(TM) i7 CPU X 980 @ 3.33GHz GenuineIntel GNU/Linux
>> mark@c2stable ~ $ zcat /proc/config.gz | grep IOMMU
>> CONFIG_GART_IOMMU=y
>> # CONFIG_CALGARY_IOMMU is not set
>> # CONFIG_AMD_IOMMU is not set
>> CONFIG_IOMMU_HELPER=y
>> CONFIG_IOMMU_API=y
>> # CONFIG_IOMMU_DEBUG is not set
>> # CONFIG_IOMMU_STRESS is not set
>> mark@c2stable ~ $
>>
>> Except for the AMD option they seem identical unless I'm misreading something.
>>
>> I'm now wondering if there is both a BIOS and chipset component to
>> making this work? I'm pretty sure I've got all the Vt-d stuff enabled
>> but I'll have to wait to go into BIOS on both of them to compare.
>>
>> I'll try to do a diff later today between both machine's .config files
>> to look for differences.
>
> Can't you simply install the Calgary IOMMU as well? I know that it
> seems IBM based stuff (I noticed it myself when I was going through
> the same process) which you probably do not need but I assume it can't
> hurt (apart from making the kernel a bit bigger). But if it fixes your
> problem... Probably worth a try.
>
>

I Agree and will try it. I was only saying I didn't previously because
all the write ups made it sound like it was for some other purpose.

I think my other question is where does this message about
CONFIG_IOMMU_SUPPORT get generated? Is it in the ebuild? If so then is
the ebuild incorrect because the option doesn't exist? Or does the
option exist but I cannot figure out how to get make menuconfig to
make it available? There are a number of web pages like this one:

http://cateee.net/lkddb/web-lkddb/IOMMU_SUPPORT.html

which seem to indicate that I should see an IOMMU option somewhere in
the drivers section of the kernel config. I do not, however, find that
right now which is why I came here to ask.

Anyway, I will be trying that later today.

Cheers,
Mark