RE: [Xen-devel] [PATCH][RFC] Support more Capability Structures andDevice Specific

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Ian Jackson wrote:
> Dong, Eddie writes ("RE: [Xen-devel] [PATCH][RFC] Support
> more Capability Structures andDevice Specific"): 
>> If we agree the basic policy is pass through except the
>> ones with known behavior, I think we don't need that
>> many case to case handle. Dexuan is working on the
>> implementation base on the summit talk and close to end,
>> maybe Yuji and Dexuan can coordinate first to see if the
>> proposed policy can server yuji's purpose. 
> 
> Is it really safe to pass through operations with unknown
> behavious ? 
> Particularly if the system has an iommu, the
> administrator may be 
> expecting the passthrough mechanism to defend the host
> from rogue 
> behaviour by the card and its owning guest.


What kind of operations in your mind will hurt host?
But yes, guest may not work properly for some cases such as some vidoe
card I mentioned in summit which may map host address to internal
register and used by drivers. For those kind of devices, CP will just
disable assignment thru kind of assignable check such as blacklist.

Other than that, I didn't see how pass through will make things worse.
Can u specify ? All guest access to memory is protected by IOMMU and
thus no imapct to host. 


Thx, eddie

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