[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 12:51 +0000, Jan Beulich wrote: > > Right. But moving the fault handling code to softirq should have already > > helped solving/mitigating that, hasn't it? > > It helps keeping Xen alive, but doesn't for any specific domain > (including Dom0). > Ok. Yes, now I remember... That was the main purpose of that work. Thanks and sorry. :-P > > 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)? > > No, I haven't - you'd have to have a device that doesn't stop I/O > after a finite amount was done (or program one that way, e.g. by > handing it a cyclic list of SG descriptors or alike). Wasn't it at your > (Citrix) end that the problem was actually observed/reported? > Yes but, as Tim said, I was never able to get in touch with the original faulting behavior/piece of hardware. Trying to simulate that as you're suggesting is basically what I did, but, at that time, I was using a passed-to-a-guest device, and wasn't bypassing (for anyone) the ~BUS_MASTERING thing... That's why I asked whether you observed a different behaviour. Anyway, I see that we're talking about different issues and understand (now) what you're trying to solve and why that is needed, so, again, sorry for dragging the discussion a bit out of scope. :-) Thanks and 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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