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[Xen-users] PCI passthrough support

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Subject: [Xen-users] PCI passthrough support
From: sanket hase <shase@xxxxxxxxxxxxxx>
Date: Sun, 25 Nov 2007 23:53:07 -0500
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Hi ,

I have been trying to understand PCI -passthrough support. Please correct me if I am wrong in my following inferences.

1. Device emulation and pass through are both implemented using split drivers. 2. But, in case of emulation drivers of dom0 are used where as in case of passthrough ( as the name suggests ) native drivers in domU are used . 3. dom0 provides a virtual PCI device { an interface for device-OPs and status of this virtual device} to domU and through associated event channel domU makes
   "synchronous" use of this device.


1. What i am really not so sure about is ... passthrough case
Will there be requirement to map the address space of this PCI device in domU ? Will the page which was being shared so-far {xen_pci_sharedinfo} for emulation , be "flipped" ( transferred ) into domU ? 2. Well , Having read the code for linux (dom0,domU) I see that there are split device drivers for PCI. (pci front and PCIback). Which are normally communicating over xenbus. which looks almost like other split drivers. How exactly then passthrough enables use of domU's drivers ? 3. And if passthrough support isnt provided how will communication between pcifront-pciback be different ? ( I guess netbsd , freebsd do not have passthrough support yet ) 4. What restricts other domUs from accessing PCI device given to other domU via passrthrough support.


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