[RFC PATCH 0/2] arm64: Add support for 48-bit Physical Addresses

[Radha Mohan]

On Wed, Nov 27, 2013 at 4:34 PM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> [CC-ing the maintainers - seems odd they were not cc-ed the first place]
>
> On 27/11/13 07:34, mohun106 at gmail.com wrote:
>> From: Radha Mohan Chintakuntla <rchintakuntla at cavium.com>
>>
>> This patch series provides an implementation of supporting 48-bit
>> Physical Addresses for ARMv8 platforms. It is the maximum width that
>> any ARMv8 based processor can support.
>>
>> The implementation extends the existing support of 40-bit PA.The kernel
>> and user space will now be able to access 128TB each. With 4KB page size
>> the Linux now will be using 4 levels of page tables by making use of
>> 'pud'. And with 64KB page size the Linux will be using 3 levels of page
>> tables.
>>
>> The code has been tested with LTP.
>
> Aside from finding out whether or not this is a useful change, this
> breaks KVM, more specifically the way kernel pages are mapped into HYP.
> Also, guests will still be limited to 40-bit IPAs, and the stage-2
> output range needs to be addressed as well.

This is useful for platforms (like ours) that will use 48-bit PAs.
Sooner or later there will
be such processors.
And yes, I haven't checked on KVM.

>
>         M.
> --
> Jazz is not dead. It just smells funny...
>