[Xen-devel] [PATCHv2 0 of 2] Deal with IOMMU faults in softirq context.

[Dario Faggioli <raistlin@xxxxxxxx>]

Hello everyone,

Reposting with after having applied the (minor) fixes suggested by Wei
and Jan.

Allen, if you can tell us what you think about this, or suggest someone
else to ask some feedback to, if you're no longer involved with VT-d,
that would be great! :-)

--

As already discussed here [1], dealing with IOMMU faults in interrupt
context may cause nasty things to happen, up to being used as a form of
DoS attack, e.g., by generating a "storm" of IOMMU faults that will
livelock a pCPU.

To avoid this, IOMMU faults handling is being moved from interrupt to
softirq context. Basically, the inerrupt handler of the IRQ originated
by an IOMMU (page) fault will raise a softirq-tasklet which will then
deal with the actual fault records by clearing the logs and re-enabling
interrupts from the offending IOMMU(s). A single tasklet is being used
even if there are more than just one IOMMU in the system, as the event
should be rare enough.

The series introduces the described mechanism for both Intel VT-d and
AMD-Vi, and has been tested on both platforms with an hacked DomU bnx2
network driver which was generating I/O page faults upon request.

Thanks and Regards,
Dario

[1] 
http://old-list-archives.xen.org/archives/html/xen-devel/2011-08/msg00638.html

--
 iommu-fault-tasklet_vtd.patch
 iommu-fault-tasklet_amd.patch

 xen/drivers/passthrough/amd/iommu_init.c |  47 
++++++++++++++++++++++++++++++++++++++++++++---
 xen/drivers/passthrough/vtd/iommu.c      |  39 
++++++++++++++++++++++++++++++++++++---
 2 files changed, 80 insertions(+), 6 deletions(-)

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-------------------------------------------------------------------
Dario Faggioli, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
PhD Candidate, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)

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