Re: [Xen-devel] frontend and backend devices and different types of hw - pci for example

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> What about other devices ? let's say a PCI sound card (or any other PCI
> device). Where is the software that should handle it ? I remember I saw
> somewhere some discussion about PCI configuration space, but I don't
> remember where.

That code is in Xen itself in Xen 2.0.  Xen controls access to the PCI 
configuration spaces so that guests can only see the devices they have access 
to.  It also controls the IO memory / ports that domains are allowed to 
access in order to control PCI devices.

Note that giving direct physical access to a PCI device has security 
implications since the guest can potentially use the cards' DMA capabilities 
to access all of physical memory.  The front/back-style devices do not have 
this limitation.

Btw, I've laid some groundwork for a virtual sound device but haven't had much 
time to hack on it yet.

Cheers,
Mark

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