Re: [Xen-devel] Superpages for VT-D

[Tim Deegan <tim@xxxxxxx>]

At 08:56 -0700 on 02 Aug (1343897810), Santosh Jodh wrote:
> Thanks for confirming. BTW, would the IOMMU ever have entries above
> domains max mapped pfn?

I don't believe so, but potentially some grant-table-style operations
might want to map pages in for DMA that don't need to be mapped in for
CPU access. 

But if you're writing a dump routine from scratch it should be easy
enough (and more efficient) to dump all the entries with a depth-first
pass over the trie, rather than individually querying all frames up to
max_mapped_pfn.

Tim.

> -----Original Message-----
> From: Tim Deegan [mailto:tim@xxxxxxx] 
> Sent: Thursday, August 02, 2012 4:11 AM
> To: Santosh Jodh
> Cc: xiantao.zhang@xxxxxxxxx; Nakajima, Jun; xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Superpages for VT-D
> 
> At 13:44 -0700 on 31 Jul (1343742260), Santosh Jodh wrote:
> > I am going to try to add this support. 
> > 
> > It looks like a new iommu_ops handler would be needed that would do 
> > the actual work of dumping the entries - one for AMD and one for 
> > Intel. Am I reading this correctly?
> 
> I think that's correct.
> 
> > Or is it better to get the root_table + paging_mode (for AMD) and 
> > pgd_maddr + agaw (for Intel) and then do a generic dump?
> 
> No; the iommu tabels are sufficiebntly arch-specific that it's best to add 
> arch-specific dump routines.
> 
> Cheers,
> 
> Tim.
> 
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