Re: [Xen-devel] [VTD][PATCH] Use bitmap to solve domain-id limitation issue

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Better. The locking is screwed but I've fixed it up and checked it in.

 -- Keir

On 5/12/07 07:25, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:

> Hi Keir,
> 
> I baked a new patch. It removes the mapping list, stores iommu domain id
> in struct hvm_iommu instead. In addition, add a spinlock to protect
> domain id bitmap. Pls review it. Thanks.
> 
> Randy (Weidong)
> 
> Keir Fraser wrote:
>> Why must a list be walked every time you want to translate
>> domid->iommu_id? Wouldn't you be better to store it in struct
>> hvm_iommu? 
>> 
>> Under what lock is the list of domid/iommu_id mappings protected?
>> Under what lock is the allocation bitmap protected (if necessary)?
>> 
>> This patch is definitely in the right direction, I just think it's
>> not fully baked yet...
>> 
>>  -- Keir
>> 
>> On 29/11/07 13:33, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
>> 
>>> The Capability register reports the domain-id width supported by
>>> hardware. For implementations supporting less than 16-bit domainids,
>>> unused bits of domain identifier field(87:72) in Context entry are
>>> treated as reserved by hardware. For example, for an implementation
>>> supporting 4-bit domain-ids, bits 87:76 of this field are treated as
>>> reserved. 16 is a small number, overflow is easy to happen. What's
>>> more, context-entries programmed with the same domain identifier
>>> must always reference the same address translation structure
>>> (through the ASR field). So Dom16 will conflict with Dom0, and
>>> device assignment fails.
>>> 
>>> This patch implements a domaid id bitmap to solve above issue.
>>> 
>>> Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
> 



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