[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] IOMMU: don't disable bus mastering on faults for devices used by Xen or Dom0
On Tue, 2012-11-06 at 09:44 +0000, Tim Deegan wrote: > > In the context of analyzing the situation described in > > "iommu=dom0-passthrough behavior" > > (http://lists.xen.org/archives/html/xen-devel/2012-11/msg00140.html) > > I suppressed the IOMMU setup for some device in Dom0, and > > was quite puzzled to find that only a single fault would occur. > > I think it would be better to allow some small number of faults per > device before disabling it rather than give dom0 carte blanche. > > This check is really there to stop a mad device from hosing the system > rather than to contain a malicious OS, and a properly out-of-control > device needs to be stopped or it will livelock Xen with iommu faults. > In a uniprocessor system, dom0 might never get the chance to fix it. > Right. But moving the fault handling code to softirq should have already helped solving/mitigating that, hasn't it? When implementing and testing that, I wasn't able to reproduce any livelock situation (although I can't exclude that to be at least partly due to my inexperience, especially at the time, with I/O virtualization)... Jan, have you (after killing the 'disable bus-mastering part' of course)? Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) Attachment:
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