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Re: [Xen-devel] Permissive devices in Xen

To: Keir Fraser <keir@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Permissive devices in Xen
From: Lukas Hejtmanek <xhejtman@xxxxxxxxxxx>
Date: Sun, 8 Jul 2007 12:00:44 +0200
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On Sun, Jul 08, 2007 at 10:55:16AM +0100, Keir Fraser wrote:
> > 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.

OK, I see. But there is problem with, e.g., InfiniBand card that during
initialization performs reset of the card. The reset destroys the PCI config
space therefore the driver reads 16 dwords from the config space and after
reset, it writes them back. In DomU, it obviously does not restore address
bars and the device fails to respond via MMIO.

So, I've tried to allow DomU (via pciback driver) to write also the address 
bars but in this case, I'm facing to huge SLAB corruptions. In Dom0 or non-Xen
kernel, it works pretty well.

Do you have any hints how to track it down?

Lukáš Hejtmánek

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