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RE: [Xen-devel] Dom0 hypercall for adding and removing PCI devices

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Dom0 hypercall for adding and removing PCI devices
From: "Han, Weidong" <weidong.han@xxxxxxxxx>
Date: Wed, 23 Jul 2008 17:26:06 +0800
Cc: joshua.levasseur@xxxxxxxxxxxxx, "Li, Xin B" <xin.b.li@xxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, espen.skoglund@xxxxxxxxxxxxx
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Thread-topic: [Xen-devel] Dom0 hypercall for adding and removing PCI devices
Keir Fraser wrote:
> On 23/7/08 10:04, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
> 
>> 1) Add a check in domain_context_unmap_one(), don't remove the device
>> from dom0 if it has RMRR. This check is added yesterday. But it's not
>> clean enough. The device is not assigned to dom0, while it is mapped
>> in dom0 VT-d page table. 
>> 
>> 2) Establish a separate RMRR page table. If the device with RMRR is
>> removed from dom0, unmap it from dom0 VT-d page table, instead map
>> it to the separate RMRR page table. This solution is clean, but it
>> introduces a new VT-d page table. Currently each domain has only one
>> VT-d page table. 
>> 
>> What's your opinions?
> 
> So this would be one extra VT-d pagetable, for the whole system,
> which would be the fallback location for RMRR mappings for devices
> which are currently not assigned to any domain? Thus allowing
> firmware to successfully initiate DMA operations on those devices?
> Sounds sensible. 
> 

Is it possible that idle_domain owns the RMRR VT-d page table?

Randy (Weidong)


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