Re: [Xen-devel] [PATCH] [VTD] Remove PCI device enumeration for dom0 in Xen

[Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>]

[Keir Fraser]
> On 22/10/08 09:59, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
>> There are already PCI probe and remove callbacks in dom0 (c/s 593 in
>> linux-2.6.18-xen.hg). So it is not necessary to enumerate devices for
>> dom0 in Xen.
>> 
>> Espen had a patch (c/s 17975) to do the same thing, but his patch was
>> reverted in order to allow old dom0 kernels to work with iommu-capable
>> platforms. Xen 3.3 has been released for a few months, I think it's time
>> to clean up it. The rebased patch is attached.
>> 
>> Keir, what's your opinion?

> Xen 3.3 should continue to work with older dom0 kernels. However,
> now that iommu is *disabled* by default, will this mean that it
> would continue to work with older dom0 kernels so long as iommu is
> not enabled on the Xen command line? This should be tested and
> confirmed with this patch applied.  If so, I would accept it.

Users of pci_lock_pdev() and pci_lock_domain_pdev() would not be able
to find the PCI device unless it has been registered by dom0.  Apart
from the iommu code, the only user affected would be the MSI code
which looks up the PCI device before enabling MSIs on it.  As such,
you would not be able to enable MSIs if you have an old dom0 kernel.

        eSk



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