Messages in this thread | | | Date | Thu, 18 Jun 2009 14:09:17 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH RFC] x86/acpi: don't ignore I/O APICs just because there's no local APIC |
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On 06/18/09 13:28, Eric W. Biederman wrote: >>> How does Xen handle domU with hardware directly mapped? >>> >>> >> We call that "pci passthrough". Dom0 will bind the gsi to a pirq as >> usual, and then pass the pirq through to the domU. The domU will bind >> the pirq to an event channel, which gets mapped to a Linux irq and >> handled as usual. >> > > Interesting. How does domU find out the pirq -> pci device mapping? >
Hm, I haven't looked at it closely, but conventionally it would be via xenbus (which is how all the split frontend-backend drivers communicate).
>> It is already; once the pirq is prepared, the process is the same in >> both cases. >> > > I 3/4 believe that. map_domain_pirq appears to setup a per domain > mapping between the hardware vector and the irq name it is known as. > So I don't see how that works for other domains. > > msi is setup on a per domain basis. >
Ah, OK. The pirq is set up for a specific domain rather than being global (otherwise it would need some kind of "which domain can access which pirq" table). dom0 can either create a pirq for itself or someone else, and the final user of the pirq binds it to a domain-local evtchn.
I think. I really haven't looked into the pci-passthrough parts very closely yet.
J
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