Re: [Xen-devel] [PATCH=v3 1/8] xen: arm: map memory as inner shareable.

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 03/17/2014 02:53 PM, Ian Campbell wrote:
> The inner shareable domain contains all SMP processors, including different
> clusters (e.g. big.LITTLE). Therefore this is the correct thing to use for Xen
> memory mappings. The outer shareable domain is for devices on busses which are
> coherent and barrier-aware (e.g. AMBA4 AXI with ACE). While the system domain
> is for things behind bridges which are not.
> 
> One wrinkle is that Normal memory with attributes Inner Non-cacheable, Outer
> Non-cacheable (which we call BUFFERABLE) must be mapped Outer Shareable on ARM
> v7. Therefore change the prototype of mfn_to_xen_entry to take the attribute
> index so we can DTRT. On ARMv8 the sharability is ignored and considered to
> always be Outer Shareable.
> 
> Don't adjust the barriers, flushes etc, those remain as they were (which is
> more than is now required).  I'll change those in a later patch.
> 
> Many thanks to Leif for explaining the difference between Inner- and
> Outer-Shareable in words of two or less syllables, I hope I've replicated that
> explanation properly above!

Is there any reason to not modify VTCR_EL2?

Regards,

-- 
Julien Grall

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