- Disable Intel IOMMU by default.

Reindl Harald h.reindl at thelounge.net
Mon Dec 19 15:05:48 UTC 2011

Am 19.12.2011 15:33, schrieb Adam Jackson:
>> * Thu Dec 15 2011 Dave Jones <davej at redhat.com>
>> - Disable Intel IOMMU by default.
> So I would assume that means that the Intel IOMMU is disabled by default
> now.
> If what you're asking is "why", I'd hazard that it's because either the
> hardware or the driver are buggy, so it's worth protecting people from.
> Which I can personally attest to, since we've had to fix the graphics
> driver's interaction with IOMMU a couple of times now and it's still not
> perfect.
>> can this introduce this old KB of VMware?
>> http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2269
> Not that this is a vmware support forum, but I'm pretty sure that kb
> article says that disabling the IOMMU is a workaround for an issue.  So
> I'm not sure what you're worried about.

about this below on guests with 8 GB RAM and 6 GB innodb_buffer_pool

You might see a guest panic message, such as Kernel panic: pci_map_single: high
address but no IOMMU. This message means that some device drivers in the guest
cannot handle more than 4GB without an IOMMU. Upgrade to one of the kernels listed
in Upgrading to a Supported Kernel (above), or limit your virtual machine to less
than 4GB of memory.

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