Re: RFC -- virtualisable NIC support in Xen

[Greg Law <glaw@solarflare.com>]

Caitlin Bestler wrote:
>  
> 
> 
>>-----Original Message-----
>>From: Greg Law [mailto:glaw@solarflare.com] 
>>Sent: Friday, September 22, 2006 4:05 AM
>>To: Caitlin Bestler
>>Cc: xen@solarflare.com; xen-devel@lists.xensource.com
>>Subject: Re: [Xen-devel] RFC -- virtualisable NIC support in Xen
>>
>>Caitlin Bestler wrote:
>>
>>>When the App/DomU posts a buffer (for TX or RX), what 
>>
>>address does it 
>>
>>>use, and how does the hardware understand it?
>>
>>It uses a "buffer address".  This is essentially an index 
>>into a "buffer-table" which is stored on the NIC.  This table 
>>is used to lookup physical addresses that the NIC will DMA to/from.
>>
>>The buffer-table is programmed from Dom0.
>>
>>The buffer-table is effectively our IOMMU/page-tables.
>>
> 
> 
> Over what scope is the buffer handle unique?

The buffer table is per NIC.  The handle into that buffer table is tied to a 
particular Virtual Interface, meaning a guest driver can only DMA to/from 
buffers associated with the virtual interface to which it has access (the VIs 
are all mapped page aligned so that the usual paging can be used to prevent one 
guest from accessing the VI of another).

Can I ask what your interest is here?  Do you think Broadcom might be interested 
in the kind of model we're proposing?

Cheers,

Greg