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Re: [Xen-devel] Permissive devices in Xen

To: Lukas Hejtmanek <xhejtman@xxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Permissive devices in Xen
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Sun, 08 Jul 2007 10:55:16 +0100
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On 8/7/07 02:05, "Lukas Hejtmanek" <xhejtman@xxxxxxxxxxx> wrote:

> The PCI_COMMAND is handled in special way so that the device is
> enabled/disabled properly, am I right?
> 
> Why is PCI_INTERRUPT_LINE read from dev->irq and not from the config space?

dom0 will have correctly routed the interrupt,a nd stored the correct irq
number in dev->irq. The number in the config space may not be correct, or
may indicate only the irq number for legacy PCI-ISA link.

> Why the PCI address bars are handled in very different way? And it seems that
> writing these bars is never committed to the real devices. Why?

domU is not trusted to manage the i/o address space. We assume dom0 has set
up the values sanely and domU should have no reason to change them.

 -- Keir


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