Re: [PATCH v3 2/7] x86/sgx: Add infrastructure to identify SGX EPC pages

[Luck, Tony]

On Fri, Jul 30, 2021 at 09:50:59AM -0700, Dave Hansen wrote:
> On 7/30/21 9:46 AM, Sean Christopherson wrote:
> > Out of curiosity, on multi-socket systems, are EPC sections clustered in a single
> > address range, or are they interleaved with regular RAM?  If they're clustered,
> > you could track the min/max across all sections to optimize the common case that
> > an address isn't in any EPC section.
> 
> They're interleaved on the systems that I've seen:
> 
> 	Socket 0 - RAM
> 	Socket 0 - EPC
> 	Socket 1 - RAM
> 	Socket 1 - EPC
> 
> It would probably be pretty expensive in terms of the physical address
> remapping resources to cluster them.

I thought xarray was overkill ... and it is ... but it makes the code
considerably shorter/simpler!

I think I'm going to go with it. Thanks to Jarkko for the suggestion.

Also added comments based on Dave's feedback on why the function is
exported, and that sgx_is_epc_page() will be slower than people might
expect.

-Tony