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

To: Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] [VTD] Remove PCI device enumeration for dom0 in Xen
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 22 Oct 2008 13:43:51 +0100
Cc: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>, "Zhao, Yu" <yu.zhao@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Han, Weidong" <weidong.han@xxxxxxxxx>
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On 22/10/08 13:38, "Espen Skoglund" <espen.skoglund@xxxxxxxxxxxxx> wrote:

>> 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.

Is there any disadvantage to keeping this legacy code in Xen, apart from it
annoyingly sitting there?

 -- Keir



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