Re: [Xen-devel] [PATCH 5/25] Xen/doc: Add Xen virtual IOMMU doc

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

On 2017年07月12日 15:26, Julien Grall wrote:
> Hi,
> 
> On 07/12/2017 04:09 AM, Lan Tianyu wrote:
>> On 2017年07月08日 00:08, Julien Grall wrote:
>>>> Because we now just have onE vIOMMU, all virtual interrupt will be
>>>> bound
>>>> to it. If need to support mult-vIOMMU, we can add device-scope
>>>> field(sbdf array or some thing like that) in the structure and specify
>>>> what devices should be under one vIOMMU.
>>>
>>> I am not sure to follow the argument here. Even if you have only one
>>> vIOMMU you need to be able to do the correspondence between the virtual
>>> MasterID (for PCI it is based on the RID) and the host MasterID.
> 
> 
>>       Sorry for later response.
>>       MasterID you mentioned here is sbdf, right? Binding between sbdf
>> and vsbdf(virtual sbdf) should be in the device pass through related
>> interface(e.g, xc_domain_bind_pt_irq_int() has already done such similar
>> thing that bind vsbdf with real interrupt of hypervisor.).
> 
> The MasterID is not the sbdf. It is an identifier based on the tuple
> (Hostbridge, Requester ID). The RequesterID (RID), might be the bdf of
> the device or something different if there is DMA aliases.
> 
> The relation between MasterID and the tuple is defined by the hardware
> and will be reported by the firmware tables.

OK. This seems ARM specific, right? From my view, Binding virtual
MasterID with physical one still should be in pass through domctl and
we may store the relationship in the hypervisor at that point.

> 
>>       vIOMMU device model can get vsbdf when guest configure vIOMMU entry
>> and hypervisor can do conversion between sbdf and vsbdf. For interrupt
>> remapping on virtual VTD, we don't find such requirement so far and got
>> enough data from IOAPIC/MSI entry and interrupt remapping entry of
>> virtual VTD. So we don't extend pass through interface.
> 
> Well, you have to think how this could be extended in the future. This
> is quite important to plan head for stable ABI.

Sure.

> Thankfully, you seem to
> use DOMCTL, so I guess we don't have to worry too much...

I try to make new vIOMMU DOMCTL general enough for all vendors.
Operations of Create/destroy and Query capabilities are necessary for
all vendor. I don't have other vendor IOMMU's knowledge and Any
suggestions are very appreciated. Thanks.

-- 
Best regards
Tianyu Lan

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