ARMv8 vs ARMv7

ARMv8 vs ARMv7

[Eric SAGNARD]

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Hi,

I am looking for informations about differences between virtualization on ARMv7 and on ARMv8.

Independently of instruction set differences and some different setup mechanisms, are there functional differences between ARMv7 hw virtualization mechanism and ARMv8 ones ? ARMv8 AArch32 is said to be fully compliant with ARMv7. From that fact, I would imagine it is correct to conclude that both virtualization mechanism are fully compatible. Is that assumption correct ? Is there some new feature available on ARMv8 that would make this architecture more interesting regarding virtualization ?

Thanks
Rgds


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Re: ARMv8 vs ARMv7

[Ian Campbell]

On Wed, 2014-08-20 at 09:59 +0200, Eric SAGNARD wrote:
> Hi, 
> 
>  
> 
> I am looking for informations about differences between virtualization
> on ARMv7 and on ARMv8. 
> 
>  
> 
> Independently of instruction set differences and some different setup
> mechanisms, are there functional differences between ARMv7 hw
> virtualization mechanism and ARMv8 ones ? ARMv8 AArch32 is said to be
> fully compliant with ARMv7.

There is a chapter/appendix towards the back of the ARMv8 ARM which
lists the differences between ARMv7 and ARMv8-AArch32, but they are
pretty minor IIRC.

>  From that fact, I would imagine it is correct to conclude that both
> virtualization mechanism are fully compatible. Is that assumption
> correct ? Is there some new feature available on ARMv8 that would make
> this architecture more interesting regarding virtualization ?

They are pretty similar and Xen's support for ARMv7 and ARMv8 is pretty
much identical.

I expect most of the differences will be in the future e.g. GICv3 only
seems to be appearing on v8 systems etc. Obviously v8 supports larger
RAM and things like that.

Ian.